KR101496490B1 - Optical film, process for producing the optical film, polarizing plate, and display device - Google Patents

Abstract

By the melt soft-film forming method, even a film cast in the widthwise central portion as a thick film can be flattened in the final film thickness shape, and an optical film having excellent optical properties with excellent planarity is produced. Provided is a method for producing an optical film capable of coping with recent demands for thinning, broadening, and high quality of a protective film for a liquid crystal polarizing plate. The method for producing an optical film by the melt soft film forming method is characterized in that in the MD stretching step, the unstretched film after the nip press is stretched to 1.1 times or more and 3.0 times or less in the conveying direction (MD direction) of the same film, The relationship of 10 占 퐉? T1-T2? 200 占 퐉 is established between the film thickness T1 (占 퐉) at the widthwise central portion of the extruded web and the film thickness T2 (占 퐉) at both ends in the width direction of the same web .

Description

TECHNICAL FIELD [0001] The present invention relates to an optical film, a polarizing plate, and a display device,

The present invention relates to various functional films such as a polarizing plate protective film, a retardation film, a viewing angle enlarging film and an antireflection film used for a plasma display, And also to various functional films used in organic EL displays and the like, a production method thereof, and a polarizing plate and a display using the optical film.

BACKGROUND ART [0002] In recent years, the development of lightweight, large-screen, and high-definition LCDs has progressed. As a result, the protective film for a liquid crystal polarizing plate is also becoming increasingly thinner, wider and higher in quality. A cellulose ester film is widely used as a protective film for a polarizing plate, but a film raw material having a wide film width and a long winding length has been demanded along with the recent large screen surface.

BACKGROUND ART [0002] Conventionally, elastic rolls have been used in the production of an optical film by a melt soft-film forming method in a so-called touch roll method. However, when the width of the film raw material is widened, there is a problem that even if the elastic touch roll is used, the touch roll does not uniformly touch the film surface due to warping of the roll.

When the film thickness of the film raw material is set to a convex shape from the both end portions in the width direction of the film toward the center (hereinafter referred to as a middle thick film), this problem can be solved, but the problem is that the film is deviated from the product specification . Further, when the film is formed by the touch roll method, the film is subjected to residual strain when it is strongly pressed during casting, and when this film is stretched in the stretching process, this residual strain causes stretching unevenness, .

Heretofore, in order to improve such residual distortion, the following patent documents related to a manufacturing method of an optical film using an elastic touch roll are available.

Japanese Patent Application Laid-Open No. 2006-334842

Patent Document 1 discloses a method for producing a thermoplastic film capable of suppressing occurrence of residual strain by the so-called polishing roller method to prevent stretching unevenness at the time of stretching and to obtain a film having high optical characteristics.

Patent Document 1 discloses a method of forming a cellulose acylate film by extruding a molten resin into a sheet form from a die, supplying the molten resin into a space between a pair of polishing rollers, And a roll having a surface covered with a fluorine resin is used as the polishing roller.

However, in the conventional polishing roller method, residual distortion is likely to occur in the film as the width increases. When a wide film formed by such a polishing roller method is stretched, a large stretching unevenness (stretching distribution) There is a problem in that an optical film having high optical characteristics can not be obtained. With respect to recent demands for thinning, widening, and high quality of protective films for liquid crystal polarizing plates, only using a wide- Could not be resolved.

It is an object of the present invention to solve the above-mentioned problems of the prior art, and to provide a method of controlling a film thickness of a web in a casting and a method of controlling the thickness of a web (film) It is possible to produce an optical film having excellent optical properties with good planarity, and it is possible to produce a protective film for a liquid crystal polarizing plate in recent years as thinner and wider A method for producing an optical film, a polarizing plate using the optical film, and a display device which can sufficiently cope with the demand for high quality, an optical film produced by the method, and a polarizing plate and a display device using the optical film.

As a result of intensive studies in view of the above, the present inventors have found that, in addition to the use of a touch roll made of an elastic roll, the present inventors have found that, by controlling the film thickness of a web in a cast, By combining MD stretching by a so-called heater heating method at a span of 300 mm or less, even a film cast with a middle thick film can flatten a final film thickness shape, and an optical film having excellent optical properties with good planarity can be manufactured And has come to complete the present invention.

In order to attain the above object, the invention according to Claim 1 is an extrusion molding method comprising: an extrusion step of extruding a melt mainly composed of a thermoplastic resin from a flexible die into a film form; a step of extruding the extruded film- And a MD stretching step of stretching the film after the nip press in the longitudinal direction, wherein the MD stretching step is a step of stretching the film after the nip press (탆) at the center in the width direction of the extruded web and a film thickness (Tm) at the center in the width direction of the extruded web in the extrusion step, The relation of 10 占 퐉? T1-T2? 200 占 퐉 is established between the film thicknesses at both ends in the width direction: T2 (占 퐉).

Claim 2 of the invention is a production method of an optical film as claimed in claim 1, wherein the stretching method of the film in the MD stretching step is a roll stretching method performed between two transport rolls arranged close to each other, The film is heated and softened by heating with a heater to stretch the MD at a stretch span of 50 mm or more and 300 mm or less.

The invention according to claim 3 is the manufacturing method of the optical film according to claims 1 or 2, characterized in that the touch roll is made of an elastic roll in which a thin metal plate is coated on the peripheral surface in the nip pressurizing step .

Claim 4 is an optical film production method according to any one of claims 1 to 3, wherein the thermoplastic resin is a cellulose ester.

The invention of the optical film of claim 5 is characterized in that it is produced by the method of producing an optical film according to any one of claims 1 to 4.

The invention of the polarizing plate of claim 6 is characterized in that the optical film of claim 5 is used on one side.

The invention of the display device of claim 7 is characterized in that the polarizing plate of claim 6 is used.

Claim 1 of the present invention relates to an extrusion process for extruding a melt mainly composed of a thermoplastic resin from a flexible die into a film form and a nip pressurizing process for nip pressing the extruded melt film And an MD stretching step of stretching the unstretched film after the nip pressure is stretched in the longitudinal direction, wherein in the MD stretching step, the unstretched film after the nipping pressure is applied to the same film T1 (占 퐉) at the center in the width direction of the extruded web and the film thickness (占 퐉) at both ends in the width direction of the same web in the extrusion step, : T2 (占 퐉), a relation of 10 占 퐉? T1-T2? 200 占 퐉 is established,

According to the invention of claim 1, in addition to the use of a touch roll made of an elastic roll, the film thickness control of the web in the casting and the MD stretching of the web (film) by the so-called heater heating method are combined, It is possible to flatten the final film thickness shape even in the case of a film cast with a middle thick film and to produce an optical film having excellent planarity and excellent optical characteristics. In recent years, there has been a demand for a thinner, broader, and higher quality protective film for a liquid crystal polarizing plate It is possible to sufficiently cope with the problem.

Claim 2 of the invention is a production method of an optical film as claimed in claim 1, wherein the stretching method of the film in the MD stretching step is a roll stretching method performed between two transport rolls arranged close to each other, The film is heated and softened by heating to heat the MD to stretch the MD at a stretching span of 50 mm or more and 300 mm or less in the stretching span of the film. According to the invention of claim 2, even a film cast with a middle- It is possible to produce an optical film having excellent optical properties with good planarity.

Claim 3 of the invention is a manufacturing method of an optical film according to claim 1 or claim 2, wherein in the nip pressurizing process, the touch roll is made of an elastic roll having a metal thin plate coated on its circumferential surface, According to the third aspect of the present invention, since the touch roll made of the elastic roll has moderate elasticity, the touch roll is deformed in conformity with the film thickness of the film cast by the middle thick film, so that the pressure unevenness hardly occurs, An optical film having optical properties can be produced.

The invention according to claim 4 is the process for producing an optical film according to any one of claims 1 to 3, wherein the thermoplastic resin is a cellulose ester, and according to claim 4 of the invention , An optical film having excellent planarity and excellent optical characteristics can be produced.

The invention of the optical film of claim 5 is produced by the method of producing an optical film according to any one of claims 1 to 4. According to claim 5 of the invention, And has excellent optical properties. By using this optical film, it is possible to sufficiently cope with recent demands for thinning, broadening, and high-quality of the protective film for a liquid crystal polarizing plate.

According to the invention of the polarizing plate of claim 6, since the optical film of claim 5 is used on one side of the polarizing plate of claim 6, when the polarizing plate of claim 6 is inserted into the display device, Easy to see).

Since the invention of the display device of Claim 7 is the use of the polarizing plate of Claim 6, the display device of claim 7 has the advantage that the visibility (viewability of the screen) is excellent .

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic flow sheet showing an embodiment of an apparatus for carrying out the method for producing an optical film of the present invention. Fig.
Fig. 2 is an enlarged flow sheet of a main portion of the manufacturing apparatus of Fig. 1, showing an enlarged view of a cooling roll portion from a flexible die. Fig.
Fig. 3 is a flow sheet showing the details of the MD stretching band of Fig. 1; Fig.
Fig. 4 is a schematic enlarged cross-sectional view of a web (film), in which Fig. 4 (a) shows a state before MD stretching, and Fig. 4 (b) shows a state after MD stretching.
5 is a partially enlarged schematic side view for explaining the MD stretching state of the web (film) in the MD stretching zone;

Best mode for carrying out the present invention will be described below with reference to the drawings, but the present invention is not limited to these.

The method for producing an optical film by the melt flexible film forming method of the present invention comprises an extrusion step of extruding a melt containing a thermoplastic resin as a main component from a flexible die into a film form and a step of extruding the extruded film- And a MD stretching step of stretching the unstretched film in the longitudinal direction after the nip pressurization.

Conventionally, when an optical film is formed by such a touch roll method, use of an elastic roll has been proposed so as not to leave as much residual distortion as possible.

However, when a recent wide-width film is formed by a touch roll method, even if an elastic touch roll is used, the film is strongly pressed and held by the warp of the film in the width direction end portion, A difference occurs.

In order to eliminate this pressure difference, 1. use more elastic rolls, 2. attach a crown to the roll, 3. use a thicker film in the middle of the raw material film portion, but the elasticity of the elastic rolls is affected by the surface roughness and processability And the crown roll has a limitation in view of scratching due to the difference in the roll peripheral speed. Thus, it has been difficult to realize a method in which the raw material film is made thicker as the center portion becomes thicker in view of the product specification (standard).

Therefore, in the present invention, in the MD stretching process, the unstretched film after the nip pressure is stretched to 1.1 times or more and 3.0 times or less in the conveying direction (MD direction) of the same film (탆) at the center in the width direction of the extruded web and the thickness T2 (占 퐉) at the both ends in the width direction of the same web in the extrusion process, and the relationship of 10 占 퐉? T1-T2? 200 占 퐉 .

For example, when a wide-width optical film having a width of 1500 mm or more and 4000 mm or less, preferably 1500 mm or more and 2500 mm or less, is formed by touch roll method, there is a difference in pressure applied to the film at the center portion and the end portion of the film, If it becomes a cause, it will not be able to do correction well.

The effect of this warpage can be canceled (solved) by making the central portion of the film 10 to 200 mu m thicker than the end portion.

However, in general, it is required to suppress the film thickness deviation in the width direction of the optical film to 5 mu m or less, preferably about 2 mu m. As a result of examining a method of filling the gap, , It was found that it is possible to make the film thickness in the final width direction of the film a flat shape by stretching the film by 1.1 to 3.0 times in the longitudinal direction (conveying direction) thereof (MD stretching).

Here, the amount by which the center portion in the widthwise middle portion of the film is used as the thick film is appropriately adjusted according to the roll width, the roll elasticity, the film width, the film viscosity, etc. When the thick film amount at the central portion in the film width direction is less than 10 mu m, A sufficient effect can not be obtained. On the contrary, if the amount of the thick film exceeds 200 mu m, there is a risk of scratching the film due to the difference in the peripheral speed of the roll, which is not preferable.

In the method for producing an optical film of the present invention, the stretching method in the MD stretching process is a roll stretching method performed between two transport rolls arranged close to each other. And the effective stretching span for MD stretching the unstretched film is 50 mm or more and 300 mm or less.

As a condition for the MD stretching in this way, it is necessary to set the effective stretching span to 50 to 300 mm. In order to clear the stretching span, the roll stretching method in which MD stretching is performed between two adjacent rolls is advantageous .

In order to make the effective stretching span less than 50 mm, a space for installing a heating device such as a heater is limited and a small roll diameter is required, so that a large stretching stress does not occur and the production speed increases.

If the effective stretching span exceeds 300 mm, the width shrinkage due to the MD stretching becomes large, which may cause a trouble in the widening, which is not preferable.

Further, in the method for producing an optical film of the present invention, it is preferable that the touch roll is formed of an elastic roll in which a metal thin plate is coated on the peripheral surface in the nip pressurizing step.

That is, when the pressure of the touch roll becomes uneven, orientation irregularity occurs in the film, and this results in non-uniformity of light and shade under Cross Nicol. In order to calibrate the film with a uniform pressure, an elastic touch roll in which a thin metal plate is coated on the circumferential surface as described above is preferable.

Hereinafter, a method for producing an optical film according to the present invention will be described in detail.

The main material of the optical film according to the present invention is preferably a polymer film of a thermoplastic resin, which is easy to manufacture, has good adhesion to a polarizing film, optically transparent, and the like.

The polymer film having the above properties is not particularly limited, and examples thereof include cellulose ester films such as cellulose diacetate film, cellulose triacetate film, cellulose acetate butyrate film and cellulose acetate propionate film, polyester film , A polycarbonate film, a polyarylate film, a polysulfone (including polyethersulfone) film, a polyester film such as polyethylene terephthalate and polyethylene naphthalate, a polyethylene film, a polypropylene film, a cellophane, (Trade name, produced by Nippon Zeon Co., Ltd.), Zeonoa (trade name, manufactured by Nippon Zeon Co., Ltd.), polyvinyl alcohol film, ethylene vinyl alcohol film, syndiotactic polystyrene film, polycarbonate film, cycloolefin polymer film, Ltd.), polymethyl X may be a film, a polyether ketone film, polyether ketone imide film, a polyamide film, a fluorine resin film, a nylon film, polymethyl methacrylate film, an acrylic film or a glass plate or the like. Among them, a cellulose ester film, a cycloolefin polymer film, a polycarbonate film, and a polysulfone (including a polyethersulfone) film are preferable, and in the present invention, a cellulose ester resin film or a cyclic olefin film A resin film containing 80% or more of an addition polymer is preferably used from the viewpoints of production cost, cost, transparency, adhesiveness, and the like.

The material constituting the optical film of the present invention includes these resins, a stabilizer, a plasticizer, an ultraviolet absorber, a matting agent as a lubricant, and a retardation control agent as necessary. These materials are appropriately selected according to the required properties of the objective optical film.

[Cellulose Resin]

When a cellulose resin is used as the material of the optical film of the present invention, the cellulose resin has a structure of cellulose ester and has a structure of at least any one of a fatty acid acyl group and a substituted or unsubstituted aromatic acyl group, Or a mixed acid ester (hereinafter simply referred to as " cellulose resin ") and amorphous. The term " amorphous " means a material which is not crystallized in an irregular molecular arrangement but becomes a solid, and shows the crystal state at the time of raw material.

Examples of the cellulose resin useful for the use of the present invention are illustrated below, but the present invention is not limited thereto.

When the cellulose resin comprises an aromatic acyl group, when the aromatic ring is a benzene ring, examples of the substituent of the benzene ring include a halogen atom, a cyano, an alkyl group, an alkoxy group, an aryl group, an aryloxy group, an acyl group, a carbonamido group, An alkenyl group, an alkynyl group, an alkylsulfonyl group, an arylsulfonyl group, an aryloxycarbonyl group, an aryloxycarbonyl group, an aralkyloxycarbonyl group, a carbamoyl group, a sulfamoyl group, an acyloxy group, an alkenyl group, An aryloxysulfonyl group, an alkylsulfonyloxy group, and an aryloxysulfonyl group.

Examples of the substituent of the benzene ring include -S-R, -NH-CO-OR,

Wherein R is an aliphatic group, an aromatic group or a heterocyclic group.

The number of substituents is 1 to 5, preferably 1 to 4, more preferably 1 to 3, still more preferably 1 or 2. When the number of substituents to be substituted with an aromatic ring is 2 or more, they may be the same or different from each other, but they may also be connected to each other to form a condensed polycyclic compound (e.g., naphthalene, indene, indane, phenanthrene, quinoline, isoquinoline , Chromene, chroman, phthalazine, acridine, indole, indoline, etc.) may be formed.

As the substituent, a halogen atom, a cyano, an alkyl group, an alkoxy group, an aryl group, an aryloxy group, an acyl group, a carbonamido group, a sulfonamide group and a ureido group are preferable, and a halogen atom, a cyano, an alkyl group, More preferably a halogen atom, a cyano, an alkyl group, an alkoxy group and an aryloxy group, and most preferably a halogen atom, an alkyl group and an alkoxy group.

The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

The alkyl group may have a cyclic structure or branch. The number of carbon atoms of the alkyl group is preferably from 1 to 20, more preferably from 1 to 12, still more preferably from 1 to 6, most preferably from 1 to 4.

Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, t-butyl, hexyl, cyclohexyl, octyl and 2-ethylhexyl.

The alkoxy group may have a cyclic structure or a branch. The number of carbon atoms of the alkoxy group is preferably from 1 to 20, more preferably from 1 to 12, still more preferably from 1 to 6, most preferably from 1 to 4. The alkoxy group may be further substituted with another alkoxy group. Examples of alkoxy groups include methoxy, ethoxy, 2-methoxyethoxy, 2-methoxy-2-ethoxyethoxy, butyloxy, hexyloxy and octyloxy.

The number of carbon atoms of the aryl group is preferably 6 to 20, more preferably 6 to 12. Examples of aryl groups include phenyl and naphthyl. The number of carbon atoms of the aryloxy group is preferably 6 to 20, more preferably 6 to 12.

Examples of the aryloxy group include phenoxy and naphthoxy. The number of carbon atoms of the acyl group is preferably 1 to 20, more preferably 1 to 12.

Examples of the acyl group include formyl, acetyl and benzoyl. The number of carbon atoms of the carbonamido group is preferably 1 to 20, more preferably 1 to 12.

Examples of the carbonamido group include acetamide and benzamide. The number of carbon atoms of the sulfonamide group is preferably 1 to 20, more preferably 1 to 12.

Examples of the sulfonamide group include methanesulfonamide, benzenesulfonamide and p-toluenesulfonamide. The number of carbon atoms in the ureido group is preferably 1 to 20, more preferably 1 to 12.

Examples of the ureido groups include (non-substituted) ureido groups.

The number of carbon atoms of the aralkyl group is preferably 7 to 20, more preferably 7 to 12. Examples of aralkyl groups include benzyl, phenethyl and naphthylmethyl.

The number of carbon atoms of the alkoxycarbonyl group is preferably 1 to 20, more preferably 2 to 12. Examples of the alkoxycarbonyl group include methoxycarbonyl.

The number of carbon atoms of the aryloxycarbonyl group is preferably 7 to 20, more preferably 7 to 12. Examples of the aryloxycarbonyl group include phenoxycarbonyl.

The number of carbon atoms of the aralkyloxycarbonyl group is preferably 8 to 20, more preferably 8 to 12. Examples of aralkyloxycarbonyl groups include benzyloxycarbonyl.

The number of carbon atoms of the carbamoyl group is preferably from 1 to 20, more preferably from 1 to 12. Examples of carbamoyl groups include (unsubstituted) carbamoyl and N-methylcarbamoyl.

The number of carbon atoms in the sulfamoyl group is preferably 20 or less, more preferably 12 or less. Examples of sulfamoyl groups include (unsubstituted) sulfamoyl and N-methylsulfamoyl. The number of carbon atoms of the acyloxy group is preferably 1 to 20, more preferably 2 to 12.

Examples of such acyloxy groups include acetoxy and benzoyloxy.

The number of carbon atoms of the alkenyl group is preferably 2 to 20, more preferably 2 to 12. Examples of alkenyl groups include vinyl, allyl and isopropenyl.

The number of carbon atoms of the alkynyl group is preferably 2 to 20, more preferably 2 to 12. Examples of the alkynyl group include thienyl.

The number of carbon atoms of the alkylsulfonyl group is preferably 1 to 20, more preferably 1 to 12.

The number of carbon atoms of the arylsulfonyl group is preferably 6 to 20, more preferably 6 to 12.

The number of carbon atoms of the alkyloxysulfonyl group is preferably from 1 to 20, more preferably from 1 to 12.

The number of carbon atoms of the aryloxysulfonyl group is preferably 6 to 20, more preferably 6 to 12.

The number of carbon atoms of the alkylsulfonyloxy group is preferably 1 to 20, more preferably 1 to 12.

The number of carbon atoms of the aryloxysulfonyl group is preferably 6 to 20, more preferably 6 to 12.

In the cellulose resin used in the present invention, when the hydrogen atom of the hydroxyl group portion of the cellulose is a fatty acid ester with an aliphatic acyl group, the aliphatic acyl group has 2 to 20 carbon atoms, specifically, acetyl, propionyl, butyryl, isobutyl Lysine, valeryl, pivaloyl, hexanoyl, octanoyl, lauroyl, stearoyl and the like.

Here, the aliphatic acyl group also includes those having a substituent. Examples of the substituent include those exemplified as the substituent of the benzene ring when the aromatic ring is a benzene ring in the above-mentioned aromatic acyl group.

In the case of producing a retardation film as an optical film, at least one selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate and cellulose phthalate is used as the cellulose resin .

Particularly preferred cellulose resins among these are cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate and cellulose acetate butyrate.

Cellulose acetate propionate or cellulose acetate butyrate, which is a mixed fatty acid ester, has an acyl group having 2 to 4 carbon atoms as a substituent, a substitution degree of an acetyl group as X and a substitution degree of a propionyl group or a butyryl group as Y , It is preferable to satisfy the following equations (1) and (2) at the same time. The substitution degree is defined as the number of hydroxyl groups substituted with an acyl group in terms of glucose units.

In particular, cellulose acetate propionate is preferably used.

Among them, it is preferable that 0.5? X? 2.5 and 0.5? Y? 2.5. More preferably, 1.0? X? 2.0 and 1.0? Y? 2.0.

The portion which is not substituted with the acyl group usually exists as a hydroxyl group. These can be synthesized by a known method.

The raw cellulose of the cellulose resin used in the present invention may be either a wood pulp or a cotton linter. The wood pulp may be either a softwood or a hardwood, but a softwood is more preferable. A cotton linter is preferably used from the viewpoint of peelability at the time of film formation. The cellulose resin produced from these can be mixed appropriately or used alone.

It is preferable that the cellulose resin used in the present invention has a small amount of foreign matter in the spots when the film is made into a film. A spots foreign material is a substance in which two polarizing plates are arranged orthogonally (Cross Nicol), a cellulose ester film is disposed therebetween, and when the slow axis of the polarizing plate protective film is positioned parallel to the transmission axis of the polarizing plate on one light source side Means a foreign substance that causes light to leak when observed at a position perpendicular to the outer surface of the other polarizing plate. At this time, it is preferable that the polarizing plate used for the evaluation is composed of a protective film free from foreign matters of dew point, and a glass plate is preferably used for protecting the polarizer. It is considered that one of the causes is that the esterified portion of the hydroxyl group contained in the cellulose resin is unreacted. The use of a cellulose resin having a small amount of foreign matter at the time of spotting, a method of removing foreign matter by filtering the heat- It is possible to reduce the foreign matter of the spots. In addition, the thinner the film thickness, the smaller the number of spots of foreign matter per unit area. The smaller the content of the cellulose resin contained in the film is, the smaller the foreign matter of the spots tends to be.

As the number of spots, the area is 250mm ² or more than 300, 50㎛ bending point 0 individual is preferred when the sugar, observing the crossed-Nicol polarizing state in size from 5 to 50㎛ the bent point on the film to be recognized. And more preferably 200 or less of the luminous points of 5 to 50 mu m.

If the luminescent spot is large, the image of the liquid crystal display is seriously adversely affected. When the retardation film functions as a polarizing plate protective film, the presence of this luminescent spot is a factor of confusion of birefringence, and adverse effects on the image are large.

In the case of removing the foreign matter by dew point filtration, it is possible to continuously carry out the process of forming the molten soft spontaneously, including the step of removing the foreign matter of spots.

In the case of using a plasticizer and a cellulose resin as a composition to be described later, the melt soft film-forming method involving a filtration step of a foreign matter by hot melting is preferable from the viewpoint of lowering the heat melting temperature, It is a preferable method from the viewpoint of improving the removal efficiency of foreign matters and avoiding thermal decomposition. Further, as another additive to be described later, an ultraviolet absorber or a mat material may be properly mixed and filtered as well.

As the filter material, conventionally known ones such as glass fiber, cellulose fiber, filter paper, and fluororesin such as tetrafluoroethylene resin are preferably used, and ceramics, metal and the like are particularly preferably used. The absolute filtration accuracy is not more than 50 mu m, preferably not more than 30 mu m, more preferably not more than 10 mu m, further preferably not more than 5 mu m. These may be used in appropriate combinations. The filter material may be of either a surface type or a depth type, but a deep type is preferable because it is less likely to be clogged.

In another embodiment, at least one of the constituent materials, at least in the cellulose resin, is subjected to filtration in the form of a solution in the form of a solution in at least one of the latter steps of the synthesis of the material and the step of obtaining the precipitate, It is also possible to remove foreign matters from the spots through the process. At this time, it is preferable that a stabilizer is present in the cellulose resin, and the plasticizer or other additives described later are dissolved in a solvent together with an ultraviolet absorber and a matting agent, and then the solvent is removed and dried, The solid content of the film constituting material may be obtained.

Further, in order to make the solution state, a process of cooling the constituent material to -20 캜 or lower in a dissolving process in a solvent may be interposed. The addition (s) of any one or more of stabilizers, plasticizers and other additives to the cellulose resin is not particularly limited in the process of synthesis (production) of the cellulose resin used in the present invention, The filtration is performed in order to separate the floating foreign matter or insoluble matter in the solution state at least once until the latter stage of the filtration, and then the other additives are added, and the solid content may be separated and dried by removal of the solvent or acid precipitation, The powdery film-constituting material mixed with the powder may be obtained.

Uniform mixing of a constituent material other than the cellulose resin of the film constituting material with the resin can contribute to imparting uniform meltability in the melting property upon heating.

A polymer material other than a cellulose resin or an oligomer may be appropriately selected and mixed with a cellulose resin. Such a polymer material or oligomer is preferably excellent in compatibility with a cellulose resin, and has a transmittance of 80% or more, preferably 90% or more, more preferably 92% or more, over the entire visible region (400 nm to 800 nm) % Or more. The purpose of mixing at least one polymer material other than the cellulose resin or oligomer is to control the viscosity at the time of heating and melting and to improve film properties after film processing. The polymer material and oligomer may be grasped as a concept as other additives.

[Cycloolefin polymer film]

The cycloolefin polymer film preferably used in the present invention will be described.

The cycloolefin polymer used in the present invention is composed of a polymer resin containing an alicyclic structure.

A preferred cycloolefin polymer is a resin obtained by polymerizing or copolymerizing a cyclic olefin. Examples of the cyclic olefin include norbornene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidene tetracyclododecene, tetracyclo [7.4.0.110, 13.02,7] trideca-2,4,6, Unsaturated hydrocarbons having polycyclic structures such as 11-tetraene and derivatives thereof; Cyclopentene, cyclohexene, 3,4-dimethylcyclopentene, 3-methylcyclohexene, 2- (2-methylbutyl) -1-cyclohexene, cyclooctene, 3a, 5,6,7a- -4,7-methano-1H-indene, cycloheptene, cyclopentadiene, cyclohexadiene, and derivatives thereof. These cyclic olefins may have a polar group as a substituent. Examples of the polar group include a hydroxyl group, a carboxyl group, an alkoxyl group, an epoxy group, a glycidyl group, an oxycarbonyl group, a carbonyl group, an amino group, an ester group and a carboxylic anhydride group. In particular, an ester group, a carboxyl group or a carboxylic acid anhydride group Do.

The preferred cycloolefin polymer may be a copolymer obtained by addition-copolymerizing a monomer other than the cyclic olefin. Examples of the addition-copolymerizable monomer include ethylene and? -Olefins such as ethylene, propylene, 1-butene and 1-pentene; Dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene and 1,7-octadiene.

The cyclic olefin is obtained by an addition polymerization reaction or a metathesis ring opening polymerization reaction. The polymerization is carried out in the presence of a catalyst. As the catalyst for addition polymerization, for example, a polymerization catalyst comprising a vanadium compound and an organoaluminum compound can be given. A polymerization catalyst comprising a halide, nitrate or acetylacetone compound of a metal such as ruthenium, rhodium, palladium, osmium, iridium or platinum as a catalyst for ring opening polymerization and a reducing agent; Or a halide or acetyl acetone compound of a metal such as titanium, vanadium, zirconium, tungsten, or molybdenum, and a polymerization catalyst comprising an organoaluminum compound. The polymerization temperature, pressure and the like are not particularly limited, but are usually polymerized at a polymerization temperature of -50 캜 to 100 캜 and a polymerization pressure of 0 to 490 N / cm ² .

The cycloolefin polymer used in the present invention is preferably a polymer obtained by polymerizing or copolymerizing a cyclic olefin, followed by a hydrogenation reaction, and changing the unsaturated bond in the molecule to a saturated bond. The hydrogenation reaction is carried out by blowing hydrogen in the presence of a known hydrogenation catalyst. Examples of the hydrogenation catalyst include cobalt acetate / triethylaluminum, nickel acetylacetonate / triisobutylaluminum, titanocene dichloride / n-butyllithium, zirconocene dichloride / sec-butyllithium, tetrabutoxy titanate / dimethylmagnesium A homogeneous catalyst comprising a combination of the same transition metal compound / alkyl metal compound; Heterogeneous metal catalysts such as nickel, palladium, and platinum; Heterogeneous solid support catalysts prepared by supporting a metal catalyst such as nickel / silica, nickel / diatomaceous earth, nickel / alumina, palladium / carbon, palladium / silica, palladium / diatomaceous earth or palladium / alumina on a carrier.

As the cycloolefin polymer, there may be mentioned the following norbornene-based polymers. The norbornene polymer preferably has a norbornene skeleton as a repeating unit, and specific examples thereof include those disclosed in JP-A-62-252406, JP-A-62-252407, JP-A-2-133413 Japanese Patent Application Laid-Open No. 63-145324, Japanese Patent Application Laid-Open Nos. 63-264626, 1-240517, 57-8815, 5-39403 Japanese Patent Application Laid-Open Nos. 5-43663, 5-43834, 5-70655, 5-279554, and 6-206985 Those disclosed in JP-A-7-62028, JP-A-8-176411, and JP-A-9-241484 can be preferably used, but the present invention is not limited thereto. These may be used alone, or two or more of them may be used in combination.

Examples of other monomers copolymerizable with the norbornene monomer include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, ,? -Olefins having 2 to 20 carbon atoms such as 1-hexadecene, 1-octadecene and 1-eicosene, and derivatives thereof; Cycloolefins such as cyclobutene, cyclopentene, cyclohexene, cyclooctene, 3a, 5,6,7a-tetrahydro-4,7-methano-1H-indene, and derivatives thereof; Nonconjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene and 1,7-octadiene; Etc. are used. Of these,? -Olefins, particularly ethylene, are preferred.

These other monomers copolymerizable with the norbornene monomers may be used alone or in combination of two or more. When the norbornene monomer and the other monomer copolymerizable with the norbornene monomer are addition-copolymerized, the ratio of the structural unit derived from the norbornene monomer and the other monomer copolymerizable with the monomer in the addition copolymer is usually 30:70 To 99: 1, preferably from 50:50 to 97: 3, and more preferably from 70:30 to 95: 5.

When the unsaturated bonds remaining in the molecular chain of the synthesized polymer are saturated by the hydrogenation reaction, the hydrogenation ratio is preferably 90% or more, more preferably 95% or more, particularly preferably 90% or more, Is 99% or more.

Examples of the cycloolefin polymer used in the present invention include thermoplastic saturated norbornene resins described in paragraphs [0014] to [0019] of JP-A No. 5-2108, and JP-A No. 2001-277430 A thermoplastic norbornene polymer described in any one of the following items [003] to [0031], a thermoplastic norbornene-based resin disclosed in paragraphs [0008] to [0045] of JP-A No. 2003-14901, The norbornene resin composition described in the publication paragraphs [0014] to [0028], the norbornene resin described in paragraphs [0029] to [0037] of Japanese Patent Application Laid-Open No. 2003-161832, A norbornene resin described in paragraphs [0027] to [0036], an alicyclic structure-containing polymer resin described in paragraphs [0009] to [0023] of JP-A-2003-211589, Patent Publication No. 2003-211588 may be mentioned the paragraphs [0008] to a norbornene polymer resin or a vinyl alicyclic hydrocarbon polymer resin described in [0024] the like.

Specifically, Zeonex, Zeonoa, JSR manufactured by Nippon Zeon Co., Ltd., Atton manufactured by JSR Kabushiki Kaisha, APEL (APL8008T, APL6509T, APL6013T, APL5014DP, APL6015T) manufactured by Mitsui Chemicals, do.

The molecular weight of the cycloolefin polymer to be used in the present invention is appropriately selected depending on the purpose of use, but the molecular weight of the cycloolefin polymer (toluene solution when the polymer resin is not dissolved) measured by gel permeation chromatography is in the range of polyisoprene or polystyrene- Is suitably in the range of 5000 to 500000, preferably 8000 to 200000, and more preferably 10000 to 100000, and the mechanical strength and the moldability of the molded article are highly balanced.

The cycloolefin polymer film may contain an additive which can be generally incorporated into a plastic film as required. Examples of such additives include a heat stabilizer, a light stabilizer, an ultraviolet absorber, an antistatic agent, a lubricant, a plasticizer and a filler, and the content thereof can be selected within a range not to impair the object of the present invention.

The method of forming the cycloolefin polymer film is not particularly limited, and any of the hot melt forming method and the solution casting method can be used. The hot melt molding method can be classified into extrusion molding method, press molding method, inflation molding method, injection molding method, blow molding method, stretching molding method and the like in more detail. In order to obtain a film excellent in mechanical strength, surface precision, , An inflation molding method and a press molding method are preferable, and an extrusion molding method is most preferable. The molding conditions are appropriately selected depending on the purpose of use and the molding method. In the case of the hot melt molding method, the cylinder temperature is usually 150 to 400 占 폚, preferably 200 to 350 占 폚, more preferably 230 to 330 占 폚 Range. If the resin temperature is excessively low, the flowability is deteriorated, causing shrinkage or distortion of the film. If the resin temperature is excessively high, voids or silver streaks may be generated by thermal decomposition of the resin, May occur. The thickness of the film is usually in the range of 5 to 300 占 퐉, preferably 10 to 200 占 퐉, and more preferably 20 to 100 占 퐉. When the thickness is excessively thin, handling during lamination becomes difficult. When the thickness is too large, the drying time after lamination becomes long, and the productivity lowers.

The wet tensile strength of the surface of the cycloolefin polymer film is preferably 40 mN / m or more, more preferably 50 mN / m or more, still more preferably 55 mN / m or more. When the wet tension of the surface is in the above range, the bonding strength between the film and the polarizing film is improved. In order to adjust the wet tension of the surface, for example, corona discharge treatment, ozone spraying, ultraviolet irradiation, flame treatment, chemical treatment, and other known surface treatments can be performed.

The sheet before stretching is required to have a thickness of about 50 to 500 mu m, and the smaller the thickness unevenness is, the more preferable it is within ± 8%, preferably within ± 6%, more preferably within ± 4% to be.

The above-mentioned cycloolefin polymer film can be obtained by the same production method as the above-mentioned cellulose ester film in order to make the optical film of the present invention. Further, it can be obtained by stretching the sheet in at least one axial direction. Further, it may be a biaxial stretching in which uniaxial stretching is practically carried out, for example, uniaxial stretching in order to orient the molecule after stretching in a range not affecting the orientation of the molecule. For stretching, it is preferable to use a tenter device or the like.

In the film thus obtained, molecules can be oriented by stretching to have a retardation of a desired size. The in-plane retardation value Ro of the film at a wavelength of 589 nm is 30 to 100 nm, more preferably 40 to 70 nm. Further, the retardation value Rt in the thickness direction is 70 to 300 nm, more preferably 100 to 250 nm.

The retardation can be controlled by the retardation of the sheet before stretching, the stretch ratio, the stretching temperature, and the thickness of the stretching orientation film. When the sheet before stretching has a constant thickness, the absolute value of the retardation tends to increase with a film having a large stretching magnification, so that a stretched oriented film of desired retardation can be obtained by changing the stretching magnification.

The smaller the deviation of the retardation is, the better, and the cycloolefin polymer film of the present invention has a small deviation of retardation of 589 nm, usually within +/- 50 nm, preferably +/- 30 nm, more preferably +/- 20 nm.

The deviation and the thickness unevenness of the retardation can be reduced by using the sheet before stretching in which the deviation and the thickness unevenness are small, and by applying the stress evenly to the sheet at the time of stretching. It is preferable to conduct the stretching under an environment in which the temperature is controlled within a uniform temperature distribution, preferably within ± 5 ° C, more preferably within ± 2 ° C, particularly preferably within ± 0.5 ° C.

[Polycarbonate-based film]

There are various polycarbonate resins used for producing the optical film of the present invention. From the viewpoints of chemical properties and physical properties, aromatic polycarbonates are preferable, and bisphenol A polycarbonates are particularly preferable . Among them, a bisphenol A derivative having a benzene ring, a cyclohexane ring, or an aliphatic hydrocarbon group introduced into the bisphenol A may be used. In particular, a bisphenol A derivative obtained by using a derivative in which these groups are introduced asymmetrically to the central carbon , A polycarbonate having a structure in which anisotropy in the unit molecule is reduced is preferable. For example, two methyl groups in the central carbon of bisphenol A are substituted with benzene rings, one hydrogen in each benzene ring of bisphenol A is substituted with asymmetrically to the central carbon such as methyl group or phenyl group, Carbonate is preferred.

Specifically, it is obtained from 4,4'-dihydroxydiphenylalkane or a halogen substituent thereof by a phosgene method or an ester exchange method, and examples thereof include 4,4'-dihydroxydiphenyl methane, 4,4'- Dihydroxydiphenyl ethane, 4,4'-dihydroxydiphenyl butane, and the like.

The optical film comprising the polycarbonate resin used in the present invention may be used in combination with a transparent resin such as a polystyrene type resin, a methyl methacrylate type resin or a cellulose acetate type resin, or at least a cellulose acetate type film A polycarbonate resin may be laminated on one side.

The production method of the polycarbonate film usable in the present invention is not particularly limited. That is, a film by an extrusion method, a film by a solvent casting method, a film by a calendering method, or the like may be used. In the present invention, a polycarbonate-based film can be obtained by using any one of uniaxial stretching and biaxial stretching and by the same manufacturing method as the preferred method for producing a cellulose ester film.

The polycarbonate film used in the present invention preferably has a glass transition temperature (Tg) of 110 ° C or higher and a water absorption rate (value measured at 23 ° C under water for 24 hours) of 0.3% or lower . More preferably, the glass transition temperature (Tg) is 120 占 폚 or higher and the water absorption rate is 0.2% or lower.

In the film constituting material, at least one kind of stabilizer is added before heating or melting of a resin such as a cellulose resin or during heating and melting. The stabilizer is required to function without decomposition even at the melting temperature for film formation.

Examples of the stabilizer include hindered phenol antioxidants, acid scavengers, hindered amine light stabilizers, peroxide release agents, radical scavengers, metal deactivators, amines and the like. These are disclosed in JP-A-3-199201, JP-A-5-1907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854 And the like.

It is possible to prevent deterioration or deterioration represented by coloring or lowering of molecular weight, including decomposition reaction which is not clarified, such as prevention of oxidation of film constituting material, capture of acid generated by decomposition, decomposition reaction of radical species due to light or heat, A stabilizer is used to suppress the generation of volatile components by decomposition of the material. That is, the addition of the stabilizer in the film constituting material is excellent from the standpoint of suppressing or preventing the generation of volatile components by alteration or decomposition of the film constituting material other than the stabilizer. In addition, the stabilizer itself is also required not to generate volatile components in the melting temperature range of the film constituting material.

On the other hand, if the film constituting material is heated and melted, the decomposition reaction becomes remarkable, and the degradation of the constituent material resulting from the coloration or the decrease in the molecular weight may be accompanied by the decomposition reaction. In addition, an undesirable volatile component generated by the decomposition reaction may be accompanied by the decomposition reaction of the film constituting material.

For the purpose of avoiding deterioration or hygroscopicity of the material, the constituent material of the film can be divided into one or more kinds of pellets and preserved. The pelletization can improve the mixing property or the compatibility of the melt at the time of heating, or can ensure the optical uniformity of the obtained film.

When the film constituting material is heated and melted, the presence of the stabilizing agent is excellent from the standpoint of suppressing the deterioration of the strength based on deterioration or decomposition of the material or maintaining the inherent strength of the material.

In the case of producing a retardation film, it is preferable to include a stabilizer. In the step of imparting retardation as a retardation film in the production of a film, deterioration of the strength of the film constituting material can be suppressed, or strength inherent to the material can be maintained. If the film constituting material is receded by remarkable deterioration, the film tends to be broken in the stretching process at the time of film formation, and the retardation value as a retardation film can not be developed.

In addition, the presence of the stabilizer suppresses the formation of coloring matter in the visible light region during heating and melting, suppresses undesirable performance as a retardation film such as transmittance or haze value caused by incorporation of volatile components into the film, It is excellent in that it can disappear. The haze value is less than 1%, more preferably less than 0.5%.

There is a case where a deterioration reaction due to oxygen in the air occurs in the preservation or film-forming process of the film constituting material. In this case, a means for reducing the oxygen concentration in the air may be used besides the stabilizing action of the stabilizer. As such means, known techniques include the use of nitrogen or argon as the inert gas, the degassing operation by depressurization or vacuum, and the operation by the closed environment. At least one of these three methods may be used in combination with the method of allowing the stabilizer. By reducing the probability that the film constituting material is in contact with oxygen in the air, deterioration of the material can be suppressed.

When the retardation film is used as a polarizing plate protective film, the stabilizer described above is contained in the film constituting material from the viewpoint of improving the preservability with time for the polarizing plate and the polarizer constituting the polarizing plate.

In the liquid crystal display using a polarizing plate, if the stabilizer described above is present in the retardation film, the retention of the retardation film with the lapse of time is improved, and the optical compensation function can be expressed over a long period of time.

As the hindered phenol antioxidant compound useful for stabilizing the film constituting material at the time of thermal melting, known compounds can be used. For example, those described in US Pat. No. 4,839,405, Specification 12 to 14 And 2,6-dialkylphenol derivative compounds.

Specific examples of the hindered phenol compound include n-octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, n-octadecyl 3- butyl-4-hydroxyphenyl) -acetate, n-octadecyl 3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl 3,5- Dodecyl 3,5-di-t-butyl-4-hydroxyphenyl benzoate, neododecyl 3- (3,5-di-t-butyl- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, ethyl α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl? - ) Propionate, 2- (n-octylthio) ethyl 3,5-di-t-butyl-4-hydroxy- 4-hydroxy-phenylacetate, 2- (n-octadecylthio) ethyl 3,5-di-t- Di-t-butyl-4-hydroxy-benzoate, 2- (n-octadecylthio) ethyl 3,5- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (n-octadecylthio) ethyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, stearamide N, N- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2- (2-stearoyloxy (3-methyl-5-t-butyl-4-hydroxybenzoate) Propylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- [3- Di-t-butyl-4-hydroxyphenyl) propionate], neopentyl (3,5-di-t-butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- (3,5- , 3,5-di-t-butyl-4-hydroxyphenylacetate), pentaerythritoltetrakis- [3- (3 ', 5 -Di-t-butyl-4'-hydroxyphenyl) propionate], 1,1,1-trimethylolethane-tris- [3- (3,5- Phenyl) propionate], sorbitol hexa- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl 7- 2-stearoyloxyethyl 7- (3-methyl-5-t-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexane (3,5-di-t-butyl-4-hydroxyhydroxyphenyl) propionate, diol-bis [(3 ', 5'- Cinnamate).

The hindered phenol-based antioxidant compound is commercially available, for example, under the trade name IRGANOX-1076 and IRGANOX-1010 from Ciba Specialty Chemicals K.K.

As an acid capturing agent useful for stabilization of the film constituting material at the time of thermal melting, it is preferable that an epoxy compound described in the specification of US Pat. No. 4,137,201 is included. Such compounds are known in the art and include diglycidyl ethers of various polyglycols, in particular polyglycols derived by condensation, such as about 8 to 40 moles of ethylene oxide per mole of polyglycol, diglycidyl glycerol, Epoxidized ether condensation products, diglycidyl ethers of bisphenol A (for example, those used conventionally in combination with vinyl chloride polymer compositions and vinyl chloride polymer compositions) (For example, 4,4'-dihydroxydiphenyldimethylmethane), epoxidated unsaturated fatty acid esters (especially esters of alkyl of about 2 to about 2 carbon atoms of a fatty acid of 2 to 22 carbon atoms, Butyl epoxystearate), and the like), and various epoxidized long chain fatty acid triglycerides (e.g., those represented by compositions such as epoxidized soybean oil) Is an epoxidized plant oil and other unsaturated natural oils include (as they are now called becomes sometimes epoxidized natural glycerides or unsaturated fatty acids, these fatty acids are typically 12 to 22 that contain a carbon atom).

Additional acid-capturing agents which can be used include those described in paragraphs 87 to 105 of JP-A-5-194788.

Hindered amine light stabilizers (HALS) which are useful for stabilization of the film constituting material upon thermal melting can be used in the known compounds, for example, in the 5th to 11th columns of U.S. Patent No. 4,619,956 and U.S. Patent No. 4,839,405 2,2,6,6-tetraalkylpiperidine compounds or acid addition salts thereof, or complexes thereof with metal compounds, as described in the third to fifth columns of the specification.

Specific examples of the hindered amine light stabilizer compound include 4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-allyl-4-hydroxy-2,2,6,6- 4-hydroxy-2,2,6,6-tetramethylpiperidine, 1- (4-t-butyl-2-butenyl) Tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 1-ethyl-4-salicyloyloxy-2,2,6,6- Tetramethylpiperidine, 4-methacryloyloxy-1,2,2,6,6-pentamethylpiperidine, 1,2,2,6,6-pentamethylpiperidin-4-yl- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, 1-benzyl-2,2,6,6-tetramethyl-4-piperidinyl maleate, Di-2,2,6,6-tetramethylpiperidin-4-yl) -adipate, (di-2,2,6,6-tetramethylpiperidin- Diethyl-2,6-diethyl-piperidin-4-yl) -s sebacate, (di-1-allyl-2,2,6,6-tetramethyl- Piperidin-4-yl) -phthalate, 1-acetyl-2,2,6,6- Tetramethylpiperidin-4-yl-acetate, trimellitic acid-tri- (2,2,6,6-tetramethylpiperidin-4-yl) ester, 1-acryloyl- 2,2,6,6-tetramethylpiperidine, dibutyl-malonic acid-di- (1,2,2,6,6-pentamethyl-piperidin-4-yl) (2, 3, 6-tetramethyl-2,6-diethyl-piperidin-4-yl) -ester, dimethyl- (1-propyl-2,2,6,6-tetramethylpiperidin-4-yl) -phosphite, tris- (1-propyl- , 6,6-tetramethylpiperidin-4-yl) -phosphate, N, N'-bis- (2,2,6,6-tetramethylpiperidin- Diamine, N, N'-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -hexamethylene-1,6-diacetamide, 1-acetyl- -Cyclohexylacetamide) -2,2,6,6-tetramethyl-piperidine, 4-benzylamino-2,2,6,6-tetramethylpiperidine, N, N'-bis- , 2,6,6-tetramethylpiperidine (2,2,6,6-tetramethylpiperidin-4-yl) -N, N'-dibutyl-adipamide, N, N'- (2-hydroxypropylene), N, N'-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -p-xylylene-diamine, 4- Bis-2-hydroxyethyl) -amino-1,2,2,6,6-pentamethylpiperidine, 4-methacrylamido-1,2,2,6,6-pentamethylpiperidine, beta] - [N- (2,2,6,6-tetramethylpiperidin-4-yl)] - amino-acrylic acid methyl ester.

The amount of the stabilizer to be added is preferably 0.001% by weight or more and 5% by weight or less, more preferably 0.005% by weight or more and 3% by weight or less based on the weight of the resin such as cellulose resin, More preferably, it is 0.01 wt% or more and 0.8 wt% or less.

If the addition amount of the stabilizer is too small, the effect of the stabilizer can not be obtained because the stabilizing action is low at the time of heat melting. If the addition amount is too large, the transparency of the film is lowered from the viewpoint of compatibility with the resin, The film is sometimes undesirably detached.

It is preferable that the stabilizer is mixed before the resin is melted. The mixing may be carried out by a mixer or the like, or may be mixed in the course of producing a resin such as a cellulose resin as described above. The stabilizing agent may be adsorbed on the surface of the resin by mixing only the stabilizing agent by mixing the mixture at a temperature equal to or lower than the melting point of the resin and at or above the melting point of the stabilizing agent.

Addition of a plasticizer is preferable from the viewpoint of modification of the film such as improvement in mechanical properties, impartation of flexibility, impartation of water absorption, reduction of water permeability, and the like.

In the melt-softening film-forming method of the present invention, the use of the plasticizer is preferably carried out for the purpose of lowering the melting temperature of the film constituting material than the glass transition temperature of the resin alone such as the cellulose resin to be used, And the purpose of lowering the melt viscosity of a film constituting material containing a plasticizer than a resin such as a resin alone.

Here, in the present invention, the melting temperature of the film constituting material means a temperature at which the material is heated in a state in which the material is heated to exhibit fluidity.

When the resin alone such as a cellulose resin has a glass transition temperature lower than the glass transition temperature, fluidity for film formation is not exhibited. However, at the temperature above the glass transition temperature of the resin, the elastic modulus or viscosity decreases due to the absorption of the heat, and the fluidity is expressed. In order to lower the melting temperature of the film constituting material, it is preferable that the plasticizer to be added has a melting point or a glass transition temperature lower than the glass transition temperature of the resin such as cellulose resin because it satisfies the above object.

As the plasticizer, for example, phosphoric acid ester derivatives and carboxylic acid ester derivatives are preferably used. Further, a polymer obtained by polymerizing an ethylenically unsaturated monomer having a weight average molecular weight of 500 to 10000 described in Japanese Patent Application Laid-Open No. 2003-12859, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain or a cyclohexyl group Acrylic polymers and the like are also preferably used.

Examples of the phosphate ester derivative include triphenyl phosphate, tricresyl phosphate, and phenyl diphenyl phosphate.

Examples of the carboxylic acid ester derivatives include phthalic acid esters and citric acid esters. Examples of the phthalic acid ester derivatives include dimethyl phthalate, diethyl phthalate, dicyclohexyl phthalate, dioctyl phthalate and diethylhexyl phthalate, Include acetyltriethyl citrate and acetyl tributyl citrate.

Other examples include butyl oleate, methyl acetyl ricinoleate, dibutyl sebacate, triacetin, trimethylolpropane tribenzoate, trimethylolpropane tris (3,4,5-trimethoxybenzoate), and the like. Alkyl phthalyl alkyl glycolates are also preferably used for this purpose. The alkyl of alkyl phthalyl alkyl glycolate is an alkyl group of 1 to 8 carbon atoms. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octylphthalyl octyl glycolate, methyl phthalyl ethyl glycolate, ethyl Butyl phthalyl methyl glycolate, butyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, propyl phthalyl ethyl glycolate, methyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalyl ethyl glycolate, and the like. Methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, Phthalic anhydride, palmitic acid, palmitic acid, palmitic acid, palmitic acid, palmitic acid, palmitic acid, palmitic acid, palmitic acid, palmitic acid, palmitic acid and palmitic acid. Two or more of these alkyl phthalyl alkyl glycolates may be used in combination.

The addition amount of the plasticizer is preferably 0.5 wt% or more to less than 20 wt%, more preferably 1 wt% or more to less than 11 wt% with respect to the resin constituting the film constituting material.

Among the above plasticizers, it is preferable that no volatile components are generated during thermal melting. Specific examples thereof include nonvolatile phosphoric acid esters described in Japanese Patent Publication No. 6-501040, for example, arylene bis (diarylphosphate) esters and trimethylolpropane tribenzoate among the above exemplified compounds, Trimethylolpropane tris (3,4,5-trimethoxybenzoate), and the like, but the present invention is not limited thereto. It is required that the thermal decomposition temperature Td (1.0) of the plasticizer when the volatile component is subject to thermal decomposition of the plasticizer is higher than the melting temperature (Tm) of the film constituting material when it is defined as the temperature when the plasticizer is reduced by 1.0% by weight.

For the purpose of the addition, the amount of the plasticizer to be added to the resin such as the cellulose resin is greater than that of the other film constituent materials, and the presence of the volatile component greatly affects the quality deterioration of the obtained film. Further, the thermal decomposition temperature Td (1.0) can be measured by a commercially available differential thermogravimetric analysis (TG-DTA) apparatus.

From the viewpoint of preventing deterioration of the polarizer or the display device against ultraviolet rays, it is preferable that the ultraviolet absorber has excellent absorption ability of ultraviolet rays having a wavelength of 370 nm or less and less absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display property.

Examples of the ultraviolet absorber include an oxybenzophenone compound, a benzotriazole compound, a salicylic acid ester compound, a benzophenone compound, a cyanoacrylate compound, and a nickel complex salt compound. A benzotriazole-based compound having less coloration is preferable. The ultraviolet absorbent described in JP-A-10-182621, JP-A-8-337574, and JP-A-6-148430 may be used.

Examples of the benzotriazole ultraviolet absorber include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'- , 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5 -Chlorobenzotriazole, 2- (2'-hydroxy-3 '- (3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole , 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (straight and branched dodecyl) -4-methylphenol, octyl- 3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol- -Hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate, and the like. .

As a commercial product, TINUVIN 109, TINUVIN 171, TINUVIN 326 and TINUVIN 928 (both manufactured by Ciba Specialty Chemicals) can be used.

Examples of the benzophenone-based compound include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy- -Methoxy-4-hydroxy-5-benzoylphenylmethane), and the like, but the present invention is not limited thereto.

When the ultraviolet absorber is added, it is added in an amount of 0.1 to 20% by weight, preferably 0.5 to 10% by weight, more preferably 1 to 5% by weight based on the weight of the resin such as cellulose resin. These may be used in combination of two or more.

A matting agent may be added to the optical film for slipperiness, transportability, and ease of winding.

The matting agent is preferably as fine as possible, and examples of the fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, Calcium and the like, and crosslinked polymer fine particles.

Among them, silicon dioxide is preferable because the haze of the film can be lowered. Fine particles such as silicon dioxide are often surface-treated with an organic material, but this is preferable because it can lower the haze of the film.

Preferred examples of the organic material in the surface treatment include halosilanes, alkoxysilanes, silazane, and siloxane. When the average particle diameter of the fine particles is large, the slipping property is large. On the contrary, when the average particle diameter is small, the transparency is excellent. The average particle diameter of the secondary particles of the fine particles is in the range of 0.05 to 1.0 占 퐉. The average particle diameter of the secondary particles of the preferable fine particles is 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are preferably used for producing unevenness of 0.01 to 1.0 mu m on the film surface. The content of the fine particles is preferably 0.005 to 0.3% by weight based on the resin such as cellulose resin.

Examples of the fine particles of silicon dioxide include AEROSIL 200, 200V, 300, R972, R972V, R974, R202, R812, OX50 and TT600 manufactured by Nippon Aerosil Co., Are Aerosil 200V, R972, R972V, R974, R202 and R812. These fine particles may be used in combination of two or more. When two or more of them are used in combination, they can be mixed and used at an arbitrary ratio. In this case, fine particles having different average particle diameters or different materials, for example, Aerosil 200V and R972V may be used in a weight ratio of 0.1: 99.9 to 99.9: 0.1.

The matting agent is preferably added before the melting of the film constituting material, or is contained in the film constituting material in advance. For example, after the fine particles dispersed in a solvent and a resin such as a cellulose resin and / or other additives such as a plasticizer and an ultraviolet absorber are mixed and dispersed in advance, the solvent is volatilized, or the matting agent is pre- Lt; / RTI > By using such a film constituting material, the matting agent can be uniformly dispersed in a resin such as a cellulose resin.

The fine particles in the film to be used as the matting agent may function for the purpose of improving the strength of the film for other purposes.

As an optical film, for example, in the case of producing a retardation film, a retardation control agent may be added to adjust the retardation. As the retardation control agent, an aromatic compound having two or more aromatic rings as described in European Patent No. 911,656A2 can be used. Two or more kinds of aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes, in addition to the aromatic hydrocarbon ring, an aromatic heterocycle. It is particularly preferred that the aromatic heterocycle is an aromatic heterocycle, and the aromatic heterocycle is generally an unsaturated heterocycle. Among them, 1,3,5-triazine ring is particularly preferable.

When a stabilizer, a plasticizer and other additives added to a resin such as a cellulose resin are added, the total amount of the stabilizer, plasticizer and other additives is preferably 1% by weight or more and 30% by weight or less, more preferably 5% by weight or less based on the weight of the resin such as cellulose resin. To 20% by weight.

The film constituting material is required to have little or no volatile components in the melting and film forming process. This is for the purpose of reducing or avoiding defects in the inside of the film or deterioration of planarity of the film surface by foaming at the time of heating and melting.

The content of the volatile component when the film constituting material is melted is required to be 1% by weight or less, preferably 0.5% by weight or less, more preferably 0.2% by weight or less, and still more preferably 0.1% by weight or less. A heating loss test from 30 deg. C to 250 deg. C is obtained by using a differential thermogravimetry apparatus (TG / DTA200 manufactured by Seiko Denshi Kogyo Co., Ltd.), and the amount of heating loss is determined as the content of volatile components.

As the film constituting material to be used, it is preferable to remove the volatile component represented by water or a solvent before or at the time of film formation. The so-called known drying method can be applied, and it can be carried out by a heating method, a depressurization method, a heat decompression method, or the like, or may be carried out under an atmosphere of nitrogen or an inert gas selected from nitrogen. When these known drying methods are carried out, it is preferable for the quality of the film to be carried out in a temperature range where the film constituting material is not decomposed.

By drying the film before film formation, the generation of volatile components can be reduced, and the film can be divided and dried in the resin alone or in a mixture of resin and film constituting material with at least one kind or a mixture other than resin. The drying temperature is preferably 100 DEG C or higher. When a material having a glass transition temperature is present in a material to be dried, the material may fuse and become difficult to handle when heated to a drying temperature higher than the glass transition temperature. Therefore, the drying temperature is preferably not higher than the glass transition temperature. When a plurality of materials have a glass transition temperature, the glass transition temperature of the glass transition temperature is referred to as the lower glass transition temperature. More preferably 100 占 폚 or higher, (glass transition temperature -5 占 폚 or lower, more preferably 110 占 폚 or higher, and (glass transition temperature -20 占 폚 or lower). The drying time is preferably 0.5 to 24 hours, more preferably 1 to 18 hours, further preferably 1.5 to 12 hours. If the drying temperature is too low, the removal rate of the volatile components becomes low, and the drying takes too much time. The drying step may be divided into two or more steps. For example, the drying step may include a preliminary drying step for storing the material and a preliminary drying step performed immediately before the film formation and one week before the film formation.

The melt plasticizing method is classified into a molding method in which heating and melting are performed, and melt extrusion molding, press molding, inflation, injection molding, blow molding, stretch molding and the like can be applied. Among them, the melt extrusion method is excellent in order to obtain an optical film excellent in mechanical strength and surface precision.

Fig. 1 is a schematic flow sheet of an embodiment of an apparatus for carrying out the method of manufacturing an optical film of the present invention, and Fig. 2 is an enlarged view of a cooling roll portion from a flexible die.

2 is a graph showing the relationship between the point P1 at which the film first contacts the surface of the first cooling roll 5 and the surface of the touch roll 6 The point P 1 at which the film first contacts the surface of the first cooling roll 5 (the first cooling member for cooling) 5, The point P2 at which the film contacts the surface of the touch roll (pressurizing second rotating body) 6 may be the same.

In the present embodiment, a film mixture containing a resin such as a cellulose resin is mixed to obtain a resin mixture, and then the melt is extruded from the flexible die 4 onto the first cooling roll 5 using the extruder 1, And is circumscribed to the first cooling roll 5 and the film melted material is pressed to the surface of the first cooling roll 5 by a predetermined pressure by the touch roll 6. The second cooling roll 7 and the third cooling roll 8 are sequentially circumscribed to three cooling rolls in total, cooled and solidified, and peeled off by the peeling roll 9. The peeled film 10 is wound by the winding device 16 after gripping both ends of the film by the stretching device 12 and stretching in the width direction.

The film (resin mixture) extruded from the flexible die 4 is cooled and surface-calibrated in at least two rotating bodies having a cooling function. A rotating body in contact with the film extruded from the flexible die 4 for the first time is defined as a first rotating body, and a rotating body contacting a film for a second time is defined as a second rotating body. That is, the first cooling roll 5 corresponds to the first rotating body, and the touch roll 6 corresponds to the second rotating body. However, the first rotating body and the second rotating body are not limited to rolls, and may be a drum, a belt, or the like.

The temperature of the first cooling roll 5 is preferably set to be not higher than the glass transition temperature (Tg) of the resin mixture and higher than the melting point of the additive.

Here, the touch roll 6 is a rotating body for pinching the film against the film in the direction of the first cooling roll 5 from the opposite side of the first cooling roll (first cooling body) 5 .

The surface of the touch roll 6 is preferably a metal, and the thickness is 1 mm to 10 mm. Preferably 2 mm to 6 mm. The surface of the second rotating member is subjected to a treatment such as chrome plating and the surface roughness is preferably 0.2 S or less. The smoother the roll surface, the smoother the surface of the resulting film.

In the method for producing an optical film of the present invention, it is preferable that the touch roll 6 is made of an elastic roll in which a thin metal plate is coated on the peripheral surface in the nip pressurizing process.

That is, when the pressure of the touch roll 6 becomes nonuniform, orientation irregularity occurs in the film, and this results in nonuniformity of brightness under Cross Nicol. In order to calibrate the film with a uniform pressure, an elastic touch roll in which a thin metal plate is coated on the circumferential surface as described above is preferable.

The material of the metal on the surface of the touch roll 6 is required to be smooth, suitably elastic, and durable. Carbon steel, stainless steel, titanium, and nickel produced by an electroforming method. It is preferable to perform surface treatment such as hard chrome plating, nickel plating, amorphous chromium plating, or ceramic spraying in order to increase the hardness of the surface or to improve the peelability with the resin. The surface-finished surface is preferably further polished to have the above-mentioned surface roughness.

The touch roll 6 has a double structure of a metal outer cylinder and an inner cylinder, and has a double cylinder structure having a space for allowing a cooling fluid to flow therebetween.

The inner tube is preferably a lightweight, rigid metal inner tube made of carbon steel, stainless steel, aluminum, titanium or the like. By imparting rigidity to the inner tube, it is possible to suppress rotation and shaking of the roll. The thickness of the inner tube is 2 to 10 times as large as the outer tube, and sufficient rigidity is obtained. The inner tube may also be covered with a resin-made elastic material such as silicon or fluorine rubber.

The structure of the space through which the cooling fluid flows may be any structure capable of uniformly controlling the temperature of the roll surface. For example, the rollers may alternately make progress and return in the width direction or flow in a spiral shape, A small temperature control is possible. The cooling fluid is not particularly limited, and water or oil can be used in accordance with the temperature range to be used.

In the present embodiment, the touch roll 6, which is the second rotary member, is set to have a drum shape in which the outer diameter of the center portion is larger than the outer diameter of both end portions. Generally, the touch rolls are pressed against the film by pressing means at both ends thereof. However, in this case, there is a phenomenon that the touch roll is strongly pressed toward the end portion. By forming the roll into a drum shape, highly uniform pressurization becomes possible.

The diameter of the touch roll 6, which is the second whole, is preferably in the range of 200 mm to 500 mm. The effective width of the touch roll 6 needs to be wider than the film width to be nip pressed. By the difference between the radius of the central portion of the touch roll 6 and the radius of the end portion (hereinafter referred to as the crowning amount), it is possible to prevent unevenness of stripes or the like occurring in the center portion of the film. The crowning amount is preferably in the range of 50 to 300 mu m.

The first cooling roll 5 and the touch roll 6 are provided at positions opposite to the plane of the film so as to clamp and press the film. The first cooling roll 5 and the touch roll 6 may be in contact with the film or with the film.

In the method for producing an optical film according to the present embodiment, the conditions of melt extrusion can be carried out in the same manner as the conditions used for thermoplastic resins such as other polyesters. It is preferable to dry the material in advance. It is preferable to dry the water to 1000 ppm or less, preferably 200 ppm or less by using a vacuum or reduced pressure dryer or a dehumidifying hot air dryer.

For example, a cellulose ester resin dried under hot air or vacuum or reduced pressure is melted at an extrusion temperature of about 200 to 300 DEG C by using an extruder 1, filtered with a filter 2 of a leaf disk type, do.

When introducing the solution from the supply hopper (not shown) into the extruder 1, it is preferable to prevent the decomposition by oxidization under vacuum or in an inert gas atmosphere under reduced pressure.

If additives such as plasticizers are not mixed in advance, they may be mixed in the middle of the extruder. In order to add them uniformly, it is preferable to use a mixing device such as a static mixer 3.

It is preferable to mix additives such as a resin such as a cellulose resin and other additives such as stabilizers added as needed, before melting. The mixing may be carried out by a mixer or the like, or may be mixed in the course of producing a resin such as a cellulose resin as described above. When a mixer is used, a general mixer such as a V-type mixer, a cone screw type mixer, a horizontal cylindrical mixer, or the like can be used.

After the film constituting material is mixed as described above, the mixture may be directly melted by using the extruder 1, but once the film constituting material is pelletized, the pellet is melted in the extruder 1 The film may be formed. When the film constituting material contains a plurality of materials having different melting points, a semi-molten material having a so-called coarse-grained shape is first formed at a temperature at which only a material having a low melting point is melted and a semi-molten material is fed to the extruder 1 It is also possible to form the film by injection. When the film constituting material contains a material that is easily decomposed by heat, it is preferable to form the film directly without forming the pellet for the purpose of reducing the number of melts, or a method of forming a semi- .

As the extruder 1, various extruders available on the market can be used, but a melt-kneading extruder is preferable, and it may be a single-screw extruder or a twin-screw extruder. When direct film formation is performed without producing pellets from the film constituting material, it is preferable to use a twin-screw extruder because an appropriate kneading degree is required. However, even if a single screw extruder is used, the shape of the screw is not limited to a syphilis type, a unimelt type, By changing the kneading type screw to a kneading type kneading type kneader. As a film constituting material, when a semi-molten material having a pellet shape or a bobbin shape is used, a single-screw extruder or a twin-screw extruder can be used.

It is preferable that the cooling step in the extruder 1 and after the extrusion is carried out with an inert gas such as nitrogen gas or the pressure is reduced to lower the oxygen concentration.

The melting temperature of the film constituting material in the extruder 1 differs depending on the viscosity and the discharge amount of the film constituting material, the thickness of the sheet to be produced, and the like, but generally the glass transition temperature Tg of the film (resin mixture) Tg or more and Tg + 100 占 폚 or less, preferably Tg + 10 占 폚 or more and Tg + 90 占 폚 or less. The melt viscosity at the time of extrusion is 10 to 100,000 poise, preferably 100 to 10000 poise. The retention time of the film constituting material in the extruder 1 is preferably short, within 5 minutes, preferably within 3 minutes, more preferably within 2 minutes. The retention time depends on the type of the extruder 1 and the conditions under which the extruded material is extruded. However, the retention time can be shortened by adjusting the supply amount of the material, the L / D, the screw rotation speed,

The shape and the number of revolutions of the screw of the extruder 1 are appropriately selected depending on the viscosity of the film constituting material, the discharge amount, and the like. In the present embodiment, the shearing rate in the extruder 1 is 1 / sec to 10000 / sec, preferably 5 / sec to 1000 / sec, and more preferably 10 / sec to 100 / sec. As the extruder 1, a commercially available extruder may be used as a plastic molding machine.

The film constituting material extruded from the extruder 1 is fed to the flexible die 4 and extruded into a film form from the flexible die 4.

The melt discharged from the extruder 1 is supplied to the flexible die 4. The flexible die 4 is not particularly limited as long as it is used for producing a sheet or a film. As the material of the flexible die 4, it is preferable to spray or platematerial such as hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, ultra high strength steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide) Buffing, machining such as lapping using a grinding wheel after # 1000 number of times, planar cutting using a diamond grinding wheel of # 1000 number or more (cutting direction is perpendicular to the flow direction of the resin), electrolytic polishing, electrolytic compound polishing And the like.

The preferable material of the lip portion of the flexible die 4 is the same as that of the flexible die 4. The surface accuracy of the lip portion is preferably 0.5 S or less, more preferably 0.2 S or less.

In this embodiment, the molten resin mixture is extruded from a flexible die 4 provided in an extruder with a film-like resin, and the extruded film-like resin is brought into close contact with at least two rotating bodies to be molded and pulled.

In the method for producing an optical film according to the present invention, for example, as shown in Fig. 4A, in the extrusion process of a melt mainly composed of a thermoplastic resin, the width of the extruded web (film) Between the film thickness T1 (占 퐉) of the direction central portion 10a and the film thickness T2 (占 퐉) of both end portions 10b and 10b in the width direction of the same web (film) A relation of 200 mu m is established.

Although the burrs 11 and 11 are formed at both ends of the web 10 at the time of casting, the film F is cut into a predetermined effective width (product equivalent portion) by the slitters 13 and 13 described later, The burrs 11 and 11 at both ends of the web are removed.

Here, the amount by which the center portion in the width direction of the film is used as the thick film is appropriately adjusted according to the roll width, the roll elasticity, the film width, the film viscosity, etc. However, when the thick film amount at the central portion in the film width direction is less than 10 mu m, A sufficient effect can not be obtained. On the contrary, if the amount of the thick film exceeds 200 mu m, there is a risk of scratching the film due to the difference in the peripheral speed of the roll, which is not preferable.

1 and 2, in the method for producing an optical film according to the present invention, the temperature at which the film first comes into contact with the surface of the first cooling roll 5 and then comes into contact with the surface of the touch roll 6 The lowering is preferably within 20 캜. If the temperature drop until the film first comes into contact with the surface of the touch roll 6 after being in contact with the surface of the first cooling roll 5 is excessively large, unevenness in film thickness becomes large due to uneven shrinkage. If the temperature at the point of time when the film contacts the touch roll 6 is too low, due to the height of the viscosity of the film, the flatness of the film and the unevenness of the film thickness can be sufficiently corrected Can not.

Preferred materials for the first cooling roll 5 and the touch roll 6 include carbon steel and stainless steel. The surface precision is preferably high, and the surface roughness is set to 0.3 S or less, more preferably 0.1 S or less.

It is preferable that the touch roll 6 presses the film to the first cooling roll 5 by the pressing means. The line pressure at which the touch roll 6 presses the film at this time can be adjusted by a hydraulic piston or the like and is preferably 0.1 to 100 N / mm, more preferably 1 to 50 N / mm.

In addition, the first cooling roll 5 or the touch roll 6 may have finer diameter at both end portions of the roll or a flexible roll face in order to increase the uniformity of adhesion to the film.

When the portion from the opening of the flexible die 4 to the first cooling roll 5 is reduced to 70 kPa or less, the correction effect of the die line is more remarkably exhibited. Preferably, the reduced pressure is 50 kPa or more and 70 kPa or less. The method of keeping the pressure of the portion from the lip of the flexible die 4 to the first cooling roll 5 to 70 kPa or less is not particularly limited, but the method of covering the periphery of the roll with the pressure member from the flexible die 4, . At this time, it is preferable that the suction device is subjected to a treatment such as heating with a heater so that the device itself does not become the attachment site of the sublimate. If the suction pressure is too small, the sublimate can not be effectively sucked, so it is necessary to set the sucking pressure to an appropriate value.

In the present embodiment, the film-shaped cellulose ester resin in a molten state is sequentially supplied from the T-die 4 to the first cooling roll 5, the second cooling roll 7 and the third cooling roll 8 in sequence And cooled and solidified while being closely contacted and transported to obtain a cellulose ester based resin film (10).

In the embodiment of the present invention shown in Fig. 1, the cold-hardened nip press film 10 peeled off from the third cooling roll (fourth cooling element for cooling) 8 by the peeling roll 9 is a MD stretching Band 20 and rolled in the transport direction (MD direction).

Fig. 3 shows details of the MD stretching zone 20. 3, the nip pressed unyroxene film 10 introduced into the MD stretching zone 20 by the guide roll 41 has a preheating roll 21 before the first stretching, a preheating roll 22 before the second stretching, The preheating roll 23 before the third stretching and the preheating roll 24 before the fourth stretching reaches the stretching and preheating roll 25 and conveyed while being pressed from above by the nip roll 26, Rolled on the roll 27.

Between the stretching / preheating roll 25 and the stretching / cooling roll 27, an upper heating heater 32 and a lower heating heater 33 are disposed. The film 10 wound on the stretching / cooling roll 27 is conveyed there while being pressed thereupon by the nip roll 28, and is stretched by the MD. The film 10 is passed through the cooling roll 29 after the first stretching, the cooling roll 30 after the second stretching, and the cooling roll 31 after the third stretching, (20).

In the MD stretching process in the MD stretching zone 20, the unstretched film 10 after the nip press is stretched to 1.1 times or more and 3.0 times or less in the longitudinal direction of the film 10.

For example, when a wide optical film having a width of 1500 mm or more and 4000 mm or less, preferably 1500 mm or more and 2500 mm or less, is formed by touch roll method, there is a difference in the pressure applied to the film at the center portion and the end portion of the film, If it becomes the cause, it becomes impossible to do the correction well.

The effect of this warpage can be canceled (solved) by making the film central part thicker than the end part by 10 to 200 mu m.

However, in general, it is required to suppress the thickness deviation of the optical film in the width direction to 5 占 퐉 or less, preferably about 2 占 퐉. As a result of studying the method for filling the gap, The film is stretched by 1.1 to 3.0 times in the longitudinal direction (conveying direction) thereof (MD stretching) so that the film thickness in the final width direction of the film is made flat, for example, as shown in Fig. 4 (b) It was found that it was possible.

In the production method of the optical film of the present invention, the film stretching method in the MD stretching step is a roll stretching method performed between two transport rolls 25 and 27 arranged close to each other. As shown in Fig. 5, The real stretching span S for MD stretching the unstretched film after the nip pressurization heated and softened by the heating of the heaters 32, 33 is 50 mm or more and 300 mm or less.

In order to clear the substantial stretched span S, it is necessary to set the MD 5 between the adjacent two rolls 25 and 27 instead of the oven heating method, A roll stretching method in which stretching is performed is advantageous.

In order to make the effective stretching span S less than 50 mm, the installation space of the heating device such as a heater is limited and a small roll diameter is required, so that a large stretching stress is not produced and this causes an obstacle to an increase in production speed.

When the effective stretching span S is more than 300 mm, the width shrinkage due to MD stretching becomes large, which may be an obstacle at the time of wide spreading, which is not preferable.

Here, roll elongation in the MD stretching zone 20 will be described in detail.

First, roll stretching is a method in which the film 10 is stretched in MD by the difference in peripheral speed between the low speed roll groups 21 to 25 and the high speed roll groups 27 to 31, And is rapidly heated to the stretching temperature by the heaters 32 and 33 provided between the low speed roll groups 21 to 25 and the high speed roll groups 27 to 31 to be MD stretched and cooled in the high speed roll groups 27 to 31 And is returned to the next step.

It is preferable that the number of the preheating rolls of the low speed roll groups 21 to 25 be small in view of scratching, but the number may be selected according to the preheating temperature of the film 10, and may be 1 to 20, preferably 2 Use more than 15 rolls.

The upper limit temperature of the preheating roll group is preferably not more than the glass transition temperature (Tg) of the film 10, preferably not more than (Tg-5), in consideration of the fact that the MD is not stretched between the preheating rolls, Lt; / RTI >

The rate of temperature rise by the preheating roll group is preferably set so that the film temperature difference at the inlet side and the outlet side of each roll is 80 DEG C or lower, preferably 50 DEG C or lower, in consideration of wrinkles due to thermal expansion.

The number of cooling rolls in the high-speed roll groups 27 to 31 may be selected depending on the temperature at which cooling is performed, and one to 15 rollers, preferably 2 to 10 rollers, are used.

The upper limit temperature of the cooling roll group is preferably not higher than the glass transition temperature (Tg) of the film, preferably not higher than (Tg-5) DEG C, in consideration of not being excessively quenched.

It is preferable that the cooling rate by the cooling roll group is such that wrinkles are not generated due to heat shrinkage and that the temperature difference between the film on the inlet side and the outlet side of each roll is 100 DEG C or less.

The roll diameter of the preheating roll group and the cooling roll group is not less than 100 mm? And not more than 400 mm?, Preferably not less than 150 mm? And not more than 300 mm? From the viewpoints of roll strength and contact area (heat transfer / sliding). Particularly, the stretching rolls 25 and 27 are preferably 250 mm or less in order to shorten the stretching span S in effect.

However, in order to prevent the film from slipping and causing scratches or MD stretching between the rolls, a draw is made according to thermal expansion or heat shrinkage. The draw of a roll is 5% or less, preferably 1% or less, between adjacent rolls.

Here, the draw of the roll is (V2 - V1) / V1, which is the ratio of the main speed V1 of the roll on the low speed side to the main speed V2 of the roll on the high speed side.

In order to control the roll of the roll in the pre-heating roll group and the cooling roll group, each of them is preferably a driving roll, but some auxiliary driving rolls and pre-rolls may be used.

A planetary roller, a roll gear, or the like is suitably used for the reduction gear. In addition, a direct drive method may be used, and these may be appropriately selected depending on the system.

The roll surface roughness in the preheating roll group and the cooling roll group may be changed by changing the roll material and roughness according to the purpose. For example, a mirror-surface roll having a surface roughness of 0.5 S or less, preferably 0.2 S or less is used for a roll contacting the film at high temperature or for preventing slippage, and a surface with a surface roughness of 1.0 S or more is rough It is preferable to use a roll.

The material of the roll surface in the preheating roll group and the cooling roll group may be selected from the group consisting of ceramics surface treated with hard chrome (H-Cr), aluminum oxide, titanium oxide, chromium oxide, etc. or a composite thereof, silicon rubber such as fluorine, chloroprene, , And Teflon (registered trademark) are used.

The arrangement and interval of the rolls in the preheating roll group and the cooling roll group are preferably narrow in order to prevent MD stretching between the rolls and to prevent the film from being cooled. The distance between the peeling of the rolls from the rolls to the time of landing on the next roll is 200 mm or less, preferably 100 mm or less.

The diameters of the nip rolls 26, 28 are not particularly limited, but are preferably smaller than the stretching roll group in order to secure the space of the heater installation 32, 33.

As the material of the nip rolls 26 and 28, a rubber roll such as silicone rubber, fluororubber or chloroprene rubber which is easily deformed elastically, or a resin roll such as a fluororesin is suitably used.

It is preferable that the position of the nip rolls 26, 28 is pressed at a position where the film is peeled / landed. Further, the pressure of the nip rolls 26, 28 is 0.1 to 50 N / mm, preferably 0.5 to 20 N / mm from the viewpoints of the film being able to squeeze the film and the film not to be scratched.

The nip roll may be nipped only at the end of the film in order to prevent scratches on the film, or may be arranged in a drum shape or at a certain angle with respect to the film width direction in view of suppressing the width shrinkage.

Next, as the kind of the heaters 32 and 33, a radiant heat source such as an infrared heater, a halogen lamp heater, or a ceramic heater is preferable from the viewpoint of cleanliness, high efficiency and space saving.

The number of heaters 32, 33 may be calculated from the heater capability, MD stretching / preheating temperature, conveying speed, film thickness, thermal conductivity, and the like, and usually 1 to 12, preferably 1 to 8 are used.

It is preferable that the heights of the heaters 32 and 33 are in the vicinity of the film as long as the height of the heaters 32 and 33 can be within a range not contacting the film. For example, 5 to 100 mm, preferably 10 to 50 mm.

The output of the heaters 32 and 33 may be appropriately adjusted in consideration of the drawing temperature, the heating rate, and the like.

The stretching temperature is not lower than the glass transition temperature Tg-20 占 폚 and the melting point Tm of the film, preferably not lower than Tg and not higher than Tg + 100 占 폚, more preferably not lower than Tg + 10 占 폚 and not higher than Tg + 80 占 폚.

The MD stretching speed is 3000% / min or more and 75000% / min or less, preferably 5000% / min or more and 50000% / min or less.

Here, the MD stretching speed (% / min) is defined as follows. That is, when the main speed of the low speed side stretching roll is V1, the main speed of the high speed side stretching roll is V2, and the real stretch span is S,

MD stretching speed (% / min) = [(V2 - V1) / S] 100

Further, the interval of the MD stretching rolls is controlled such that the shorter the interval in which the film is not held by the roll, the more the width shrinkage is suppressed. Here, the distance between the centers of the rolls is 400 mm or less, preferably 300 mm or less.

The number of cleaning devices for the preheating, stretching, and cooling rolls in the MD stretching zone 20 may be one or plural, may be in-line or off-line, and may not be provided in some cases. As the cleaning means, a known roll cleaning means such as a method of wiping off the contaminants by pressing the nonwoven fabric is suitably used.

The method for producing an optical film according to the present invention is characterized in that in the MD stretching step, the unstretched film after the nip press is stretched to 1.1 times or more and 3.0 times or less in the conveying direction (MD direction) of the same film, The relationship of 10 占 퐉? T1-T2? 200 占 퐉 is established between the film thickness T1 (占 퐉) in the widthwise central portion of the extruded web and the film thickness T2 (占 퐉) at both ends in the width direction of the same web.

According to the present invention, in addition to the use of the touch roll 6 made of an elastic roll, since the film thickness control of the web in the casting and the MD stretching of the web (film) by the so-called heater heating method are combined, Even if the film is cast into the middle thick film as shown in Fig. 4 (a), the final film thickness shape can be made flat, for example, as shown in Fig. 4 (b) An optical film having excellent optical properties can be produced.

As described above, in the present invention, the stretching method of the film in the MD stretching process is a roll stretching method performed between two transport rolls 25 and 27 arranged close to each other, and the film is stretched by heating the heaters 32 and 33 And the film is MD stretched at a stretching span of 50 mm or more and 300 mm or less. Thus, even if the film is cast into the middle thick film as shown in Fig. 4 (a) For example, as shown in Fig. 4 (b), thereby making it possible to produce an optical film having excellent optical properties with good planarity.

Subsequently, the film after the MD stretching is led to a width stretching device (tenter) 12, and the film 10 is stretched in the transverse direction (width direction) there. By this width stretching, molecules in the film are oriented.

In the embodiment of the present invention shown in Fig. 1, the cooling and solidified nip pressed unoriented film 10 peeled off from the third cooling roll 8 by the peeling roll 9 is continuously stretched in the MD stretching band ( (Or in-line) that is rolled in the conveying direction (MD direction), but the present invention is not limited to this case, and the cooled and solidified nip pressed unyrondhened film 10 There is a case where the unoriented film 10 is once unwound from a winding roll in a so-called off-line, guided to the MD stretching zone 20, and then rolled in the carrying direction (MD direction).

In the case of transverse stretching (width stretching), transverse stretching is effected in which the temperature difference is sequentially increased in the range of 1 to 50 캜 in two or more stretched regions, whereby thickness and optical distribution in the width direction can be reduced .

As a method of stretching the film in the width direction, a known tenter or the like can be preferably used. In particular, the stretching direction is set to the width direction, so that lamination with the polarizing film can be carried out in a roll form. By stretching in the width direction, the slow axis of the optical film made of the cellulose ester based resin film becomes the width direction.

 On the other hand, the transmission axis of the polarizing film is usually the width direction. By inserting the polarizing plate laminated so that the transmission axis of the polarizing film and the slow axis of the optical film are parallel to each other, the display contrast of the liquid crystal display device can be increased and a satisfactory viewing angle can be obtained.

When an optical film is produced by the production method of the present invention, an optical film having a center line average roughness (Ra) of 0.1 탆 or less, further 0.05 탆 or less is obtained. In addition, the film thickness variation in the width direction (entire film width) is within ± 3%, and moreover, within ± 2% with respect to the average film thickness. The " average film thickness " means an average value of the thicknesses of the entire film except for both ends (ears) by the neck-in. The surface roughness and the film thickness variation of the film can be measured by a known method. For example, regarding the surface roughness of a film, there is a method of measuring the film surface by about 5 mm with a surface roughness meter and comparing the roughness (Ra) as an average roughness. Further, the film thickness variation can be measured by a film thickness meter to obtain a standard deviation, or it is possible to compare the variation with the average film thickness.

Although the glass transition temperature (Tg) differs depending on the film constituting material, Tg can be controlled by making the ratio of the material constituting the film and the constituent material different. When a retardation film is produced as an optical film, the Tg is preferably 120 deg. C or more, and more preferably 135 deg. C or more. In the liquid crystal display device, the temperature environment of the film changes due to the temperature rise of the apparatus itself, for example, the temperature rise from the light source, in the image display state. If the Tg of the film is lower than the environmental temperature of the film at this time, a large change is made in the retardation value derived from the orientation state of the molecules fixed in the film by stretching and the dimensional shape as the film. If the Tg of the film is excessively high, the temperature of the film constituting material becomes high when the film is made into a film. Therefore, the energy consumption for heating is increased, and the material itself is decomposed during film formation and coloring may occur. Deg.] C or less.

In the widthwise stretching process, a well-known heat-setting process, cooling, or relaxation process may be performed, or may be appropriately adjusted so as to have the properties required for the objective optical film.

In the case of producing a retardation film, the width stretching process and the heat fixing process are appropriately selected and performed in order to impart necessary functions and physical properties for enlarging the viewing angle of the liquid crystal display device. That is, when a retardation film is produced as an optical film and the function of the polarizing plate protective film is compounded, it is necessary to control the refractive index. The refractive index control can be performed by a width stretching operation, Method. Hereinafter, the width stretching method will be described.

In the widthwise stretching process of the retardation film, necessary retardations Ro and Rt can be controlled by 1.0 to 3.0 times stretching in one direction of the cellulose resin and 1.01 to 3.1 times stretching in the film surface in a direction orthogonal thereto . Here, R o represents in-plane retardation and is obtained by multiplying the thickness by the difference between the refractive index in the longitudinal direction MD and the refractive index in the transverse direction TD in the in-plane direction. R t indicates retardation in the thickness direction, The average of the direction (MD) and the width direction (TD)] and the refractive index in the thickness direction multiplied by the thickness.

The widthwise stretching can be performed, for example, sequentially or simultaneously with respect to the longitudinal direction of the film (the direction in which it is flexed and conveyed) and the direction orthogonal to it in the film plane, that is, the width direction. If the stretching ratio in at least one direction is too small, a sufficient retardation can not be obtained. On the other hand, if the stretch ratio is too large, stretching in the width becomes difficult and film breakage may occur.

The stretching in the biaxial directions orthogonal to each other is effective for putting the refractive indexes nx, ny, and nz of the film in a predetermined range. Here, nx is the refractive index in the MD direction, ny is the refractive index in the width direction TD, and nz is the refractive index in the thickness direction.

When stretching in the width direction, the refractive index may be distributed in the width direction in some cases. This distribution sometimes appears when the tenter method is used. It is considered that this phenomenon occurs when the film is stretched in the width direction to produce a contracting force at the center of the film, and the end portion is fixed, which is called a so-called bowing phenomenon. Also in this case, the stretching in the flexible direction can suppress the bowing phenomenon and reduce the distribution of the retardation in the width direction.

By stretching in the biaxial directions orthogonal to each other, variations in film thickness of the resulting film can be reduced. If the film thickness variation of the retardation film is excessively large, the retardation becomes uneven, and unevenness such as coloring may be a problem when used in a liquid crystal display.

The film thickness variation of the cellulose resin film is preferably within a range of 占 3% and 占 1%. For the above-mentioned purposes, a method of stretching in mutually orthogonal biaxial directions is effective. The stretching magnifications in the biaxial directions orthogonal to each other are 1.0 to 3.0 times in the flexible direction and 1.01 to 3.1 Fold, it is more preferable to obtain a retardation value which is required to be carried out in the range of 1.01 to 2.7 times in the direction of the flexure and 1.05 to 2.8 times in the direction of the width.

When the absorption axis of the polarizer exists in the longitudinal direction, the transmission axis of the polarizer coincides with the width direction. In order to obtain a long polarizing plate, the retardation film is preferably stretched so as to obtain a retardation axis in the width direction.

When a cellulose resin for obtaining positive birefringence with respect to stress is used, the slow axis of the retardation film can be imparted in the width direction by stretching in the width direction from the above-described constitution. In this case, in order to improve the display quality, it is preferable that the slow axis of the retardation film is in the width direction, and in order to obtain the aimed retardation value, it is preferable that the expression (stretching magnification in the width direction) ). ≪ / RTI >

After the width stretching, the end portion of the film 10 is slit with a width corresponding to the product by the slitter 13, cut and cut, and knurled by a knurling machine comprising an embossing ring 14 and a back roll 15 (Embossing) is applied to both ends of the film and is wound up by the winding device 16 to prevent adhesion and scratches in the optical film (original wound body) F.

The knurling process can be performed by heating or pressurizing a metal ring having a concavo-convex pattern on its side surface. Further, the gripping portions of the clips at both ends of the film are usually deformed and can not be used as a film product, so they are cut off and reused as a raw material.

When the retardation film is a polarizing plate protective film, the thickness of the protective film is preferably from 10 to 500 mu m. Particularly, the lower limit is 20 占 퐉 or more, preferably 35 占 퐉 or more. The upper limit is 150 mu m or less, preferably 120 mu m or less. A particularly preferable range is 25 占 퐉 or more to 90 占 퐉. If the retardation film is thick, the polarizing plate after the polarizing plate processing becomes too thick, which is not particularly suitable for the purpose of thin and light weight in the liquid crystal display used for a notebook computer or a mobile electronic device. On the other hand, if the phase difference film is thin, it is difficult to express retardation as a retardation film, and further, the moisture permeability of the film increases, and the ability to protect the polarizer from humidity is lowered.

The optical film to which the present invention is applied is a functional film used for various displays such as a liquid crystal display, a plasma display, and an organic EL display, especially a liquid crystal display, and is a polarizing plate protective film, a retardation film, An optical compensation film such as a magnifying film, and particularly a retardation film.

(Liquid crystal display device)

The polarizing plate comprising the retardation film constituted by the optical film of the present invention is capable of exhibiting a higher display quality as compared with a conventional polarizing plate and is particularly suitable for a multi-domain type liquid crystal display device, more preferably a multi- And is suitable for use in a domain type liquid crystal display device.

Multi-domainization is also suitable for improving the symmetry of image display, and various methods have been reported. Ozida, Yamauchi: Liquid crystal, 6 (3), 303 (2002). The liquid crystal display cell is described in " Yamada, Yamahara: liquid crystal, 7 (2), 184 (2003) "

The polarizing plate using the optical film of the present invention can be used in a multi-domain vertical alignment (MVA) mode represented by a vertical alignment mode, in particular, a four-divided MVA mode, a known PVA (Patterned Vertical Alignment) mode , And can be effectively used in a CPA (Cotinuous Pinned Alignment) mode in which electrode arrangement and keying ability are fused. In addition, a proposal of a film having optically biaxial property is also disclosed in the case of being suitable for an OCB (Optical Compensated Bend) mode, and is disclosed in T. Miyashita, T. Uchida: J. SID, 3 (1), 29 , And the display quality effect can be exhibited by the polarizing plate using the optical film of the present invention.

The arrangement of the liquid crystal mode and the polarizing plate is not limited as long as the display quality effect can be exhibited by the polarizing plate using the optical film of the present invention.

It is preferable that the display quality of the display cell is symmetrical with respect to the human eye. Therefore, when the display cell is a liquid crystal display cell, the domain can be multiplexed with priority given to the symmetry of the viewing side. The domain can be divided by a known method and can be determined in consideration of the properties of a known liquid crystal mode by a bipartite method, more preferably a quadruple method.

The liquid crystal display device is also applied as a device for colorization and moving picture display. Since the display quality is improved by the optical film of the present invention, the contrast is improved and the resistance of the polarizing plate is improved. It becomes.

In the liquid crystal display device, one polarizing plate including a retardation film constituted by the optical film of the present invention is arranged for each liquid crystal cell, or two polarizing plates are arranged on both sides of the liquid crystal cell. At this time, by using the retardation film side included in the polarizing plate to face the liquid crystal cell of the liquid crystal display device, it is possible to contribute to the improvement of the display quality.

In the polarizing plate, a polarizing plate protective film of a cellulose derivative is used on the surface opposite to the retardation film as viewed from the polarizer, and a general-purpose TAC film or the like can be used. The polarizing plate protective film located on the side far from the liquid crystal cell can be provided with another functional layer in view of improving the quality of the display device.

The optical film according to the present invention may be provided with functions such as anti-reflection, anti-glare, anti-scratch, anti-dust adhesion, and brightness enhancement. It may be attached to the surface of the polarizing plate, but is not limited thereto.

Generally, in the retardation film, fluctuation of Ro or Rth as the above retardation value is required to obtain stable optical characteristics. Particularly, in the liquid crystal display device of the birefringence mode, these fluctuations may cause image unevenness.

In the film produced by the solution casting method, the retardation value may fluctuate depending on the volatilization of an amount of an organic solvent remaining in an extremely small amount in the film. This film is produced, stored and transported in the form of a long wound product, and processed into a polarizing plate by a polarizing plate manufacturer or the like. Therefore, there is a case where the residual solvent is present and the volatility is lowered toward the inner side of the winding of the wound product. As a result, there is a case in which a minute difference in concentration of the residual solvent occurs from the outside of the winding to the center of the winding from the both ends to the center in the winding direction and in the width direction, and these are caused to start to cause a change and variation with time in the retardation value.

On the other hand, in the present invention, there is no solvent for volatilization in order to produce a film by the melt-blown method. As a result, a roll-shaped optical film having a small change in retardation value over time and fluctuation can be obtained.

Since the film produced by the melt-blowing method is constituted mainly of a resin such as a cellulose resin, it is possible to utilize an alkali treatment process by utilizing the inherent saponification of a resin such as a cellulose resin. When the resin constituting the polarizer is polyvinyl alcohol, a completely saponified polyvinyl alcohol aqueous solution can be used for bonding to the retardation film as in the conventional polarizing plate protective film. Accordingly, the present invention is superior in that it can apply the conventional polarizing plate processing method, and is particularly excellent in that a long-form roll polarizing plate can be obtained.

Further, according to the present invention, in the case of producing a film by using a wide flexible die 4 having a film (web) width of 1500 mm or more and 4000 mm or less at the exit of the flexible die, .

When the film (web) width of the exit of the flexible die is 1500 mm or more, it is possible to take a product having a width exceeding 2000 mm as an optical film after drawing or the like. The film (web) width of the outlet of the flexible die is in the range of 1500 mm to 4000 mm, particularly in the range of 1700 mm to 4000 mm, for the invention to exhibit the effect of obtaining a highly planar film. It is not practical that a film having a flexible width exceeding 4000 mm is expected to lower the stability in the subsequent conveying process or the like.

The present invention can produce a film having particularly high planarity when the film thickness is 15 占 퐉 to 80 占 퐉 when the film is sandwiched between the first rotating body and the second rotating body. When the thickness of the film when the nip is pressed against the first rotating body and the second rotating body is 15 탆 to 80 탆, a product of 10 탆 to 70 탆 can be formed as an optical film after drawing. When the thickness of the film when the nip is pressed against the first rotating body and the second rotating body is thinner than 15 mu m, the risk of contact between the ends of the first rotating body and the second rotating body is increased.

In the production of the retardation film, a functional layer such as an antistatic layer, a hard coat layer, an active facilitating layer, an adhesive layer, an antiglare layer, or a barrier layer may be applied before and / or after stretching. At this time, various surface treatments such as corona discharge treatment, plasma treatment and chemical solution treatment can be carried out as needed.

In the film-forming step, the clip gripping portions at both ends of the cut film may be reused as raw materials for film of the same variety or as raw materials for films of different kinds after the pulverization treatment or, if necessary, after the assembling treatment.

A composition including a resin such as a cellulose resin having a different additive concentration such as the plasticizer, ultraviolet absorber, or matting agent described above may be co-extruded to produce an optical film having a laminated structure. For example, an optical film having the same structure as the skin layer / core layer / skin layer can be formed. For example, the matting agent may be contained in the skin layer only, or only in the skin layer. The plasticizer and ultraviolet absorber may be contained in the core layer more than the skin layer and may be contained only in the core layer. The kind of the plasticizer and the ultraviolet absorber may be changed in the core layer and the skin layer. For example, a plasticizer and / or an ultraviolet absorber having low volatility may be contained in the skin layer and a plasticizer having excellent plasticity, An excellent ultraviolet absorber may be added. The glass transition temperature of the skin layer and the core layer may be different from each other and the glass transition temperature of the core layer is preferably lower than the glass transition temperature of the skin layer. At this time, the glass transition temperature of both the skin and the core may be measured, and an average value calculated from the volume fraction of the skin and the core may be defined as the glass transition temperature Tg. In addition, the viscosity of the melt containing the cellulose ester at the time of melt refining may be different between the skin layer and the core layer, or the viscosity of the skin layer may be the viscosity of the core layer, or the viscosity of the core layer may be the viscosity of the skin layer.

The optical film of the present invention has a dimensional stability of ± 2.0% in the dimensional variation at a temperature of 80 ° C and a humidity of 90% RH on the basis of the dimension of the film left to stand at 23 ° C and 55% RH for 24 hours, , Preferably less than 1.0%, and more preferably less than 0.5%.

When the optical film of the present invention is used as a retardation film for a protective film of a polarizing plate, if the retardation film itself has a fluctuation of more than the range described above, the absolute value of the retardation and the orientation angle as a polarizing plate deviate from the original setting, And the display quality may be deteriorated in some cases.

When the optical film of the present invention is used as a protective film of a polarizing plate as a retardation film, the production method of the polarizing plate is not particularly limited and can be produced by a general method. There is a method in which a polarizing plate protective film is bonded to both surfaces of a polarizer using a completely saponified polyvinyl alcohol aqueous solution on both sides of a polarizer prepared by alkali treatment of the obtained retardation film and immersion stretching of a polyvinyl alcohol film in an iodine solution, On one side, the retardation film, which is the polarizing plate protective film of the present invention, is directly bonded to the polarizer.

Instead of the above alkali treatment, the polarizing plate may be subjected to an easy adhesion process as described in JP-A-6-94915 and JP-A-6-118232.

The polarizing plate is composed of a polarizer and a protective film for protecting both surfaces of the polarizer, and a protective film is bonded to one side of the polarizing plate and a separate film is bonded to the opposite side of the polarizing plate. The protective film and the separate film are used for the purpose of protecting the polarizing plate when the polarizing plate is shipped, when the product is inspected, and the like. In this case, the protective film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the opposite side of the surface joining the polarizing plate to the liquid crystal plate. Further, the separate film is used for the purpose of covering the adhesive layer to be bonded to the liquid crystal plate, and is used on the side of bonding the polarizing plate to the liquid crystal cell.

<Examples>

Examples 1 to 6

(Resin mixture)

89% by weight of cellulose acetate propionate

(Acetyl group substitution degree: 1.4, propionyl group substitution degree: 1.35, number average molecular weight: 60000)

9% by weight of trimethylolpropane tribenzoate,

(Plasticizer, melting point 85 캜)

0.25 wt% of an antioxidant (IRGANOX XP 420 / FD)

(Manufactured by Ciba Specialty Chemicals)

UV absorber 1.6 wt%

(TINUVIN 928, manufactured by Ciba Specialty Chemicals, melting point 115 캜)

Matting agent (silica fine particles) 0.15 wt%

(Shihosta KEP-30, manufactured by Nippon Shokubai Co., Ltd., average particle diameter 0.3 mu m)

The substitution degree of the acyl group of the acetyl group, the propionyl group and the butyryl group of the cellulose acetate propionate was measured according to the method defined in ASTM-D817-96.

The above materials were mixed in a V-type mixer for 30 minutes, and then melted at 230 DEG C under a nitrogen atmosphere using a twin-screw extruder equipped with a stranded die to prepare cylindrical pellets having a length of 4 mm and a diameter of 3 mm. The glass transition point (Tg) of the obtained pellets was 135 占 폚.

The pellets were dried at 100 DEG C for 5 hours to have a water content of 100 ppm and the pellets were supplied to the single screw extruder 1 provided with the T die 4 shown in Fig. The melt contained 11 wt% of additives other than resin.

The single screw extruder 1 adjusted the number of revolutions of the screw so that the screw diameter was 90 mm, L / D was 30, and the extrusion amount was 140 kg / h. Nitrogen gas was sealed from the vicinity of the material supply port, and the inside of the extruder 1 was maintained in a nitrogen atmosphere. The temperature of the extruder 1 and the T die 4 was set at 240 캜. The T die 4 is a coat hanger type, having a width of 1900 mm, a hard chrome plating on the inner wall, and a mirror finish of 0.1 S in surface finish. The lip gap of the T die 4 was set at 2 mm.

As shown in Fig. 2, the film from the T die 4 was dropped onto a first cooling roll (first cooling body) 5 having a chrome plated mirror surface with a roll width of 2400 mm, and at the same time, The film was pressed by a touch roll (second pressurizing body) 6 having a temperature-adjusted roll width of 2400 mm.

At this time, the surface temperature of the first cooling roll (first cooling body) 5 was set to be not higher than the glass transition temperature of the resin (Tg = 135 캜), the melting point of the additive (melting point of the plasticizer 85 캜, 115 占 폚) or more. Further, the touch roll (pressurization second rotary body) 6 pressed the film at a linear pressure of 5 N / mm.

The film pressed to the first cooling roll (first cooling body) 5 and the touch roll (pressurization second rotation body) 6 is subsequently heated to a second cooling roll (third cooling body) 7) and a third cooling roll (fourth cooling for all) 8 in this order, cooling and solidifying them, and peeling off with a peeling roll 9.

The film thickness profile of the undrawn film 10 sandwiched and pressed between the touch rolls 6 is the same as the film thickness profile of the non-stretched film 10 having a width corresponding to the product of 1500 mm The lip gap was adjusted with a dice bolt so that the film thickness (T2) at the end portion was 130 mu m and the film thickness (T1) at the center portion was 200 mu m. This unstretched film 10 was once wound into a roll shape. The width of the unstretched film 10 was 1700 mm.

Thereafter, the roll-shaped film 10 was loosened and MD stretching was performed in the MD stretching zone 20 shown in Fig. 3, the nip pressed unyroxene film 10 introduced into the MD stretching zone 20 by the guide roll 41 has a preheating roll 21 before the first stretching, a preheating roll 22 before the second stretching, , The preheating roll 23 before the third stretching and the preheating roll 24 before the fourth stretching to reach the stretching and preheating roll 25 and being conveyed while being pressed from above by the nip roll 26, Rolled on the roll 27. An upper heating heater 32 and a lower heating heater 33 are disposed between the stretching / preheating roll 25 and the stretching / cooling roll 27.

The film 10 wound on the stretching / cooling roll 27 is conveyed while being pressed thereupon by the nip roll 28 there, and is stretched by the MD. The film 10 is passed through the cooling roll 29 after the first stretching, the cooling roll 30 after the second stretching and the cooling roll 31 after the third stretching, 20).

In Table 1, the numbers of the preheating, stretching and cooling rolls, the roll use, the roll diameter (mm), the material, the roughness, and the roll temperature (캜) are collectively described. In the material of the roll, &quot; H-Cr &quot; means hard chrome.

Further, the capacity of the heaters 32 and 33 was set to 50 kW, and the output was adjusted to the set drawing temperature. The height of the heaters 32 and 33 was set to 30 mm, and the pressure of the nip rolls 26 and 28 was set to 2 N / mm.

In Examples 1 to 6, in the stretching process in the MD stretching zone 20, the unstretched film 10 after being clamped and pressed was subjected to various conditions shown in Table 2 below and the length of the same film 10 Direction to 1.1 times or more and 3.0 times or less.

As shown in Table 2 below, the stretching conditions are as follows: a low speed side feed speed (m / min), a film thickness deviation T1-T2 (占 퐉), a draw ratio (times) The span (mm) was changed in each of Examples 1 to 6.

In Example 2, the actual stretching span S was shortened in Example 2. In Example 3, the effective stretching span S was elongated. In Example 4, the draw ratio was set to be low, and in Example 5, the draw ratio was set to be high. In Example 6, the effective stretching span S was made longer than that in Example 3. In Example 2, the MD stretching was carried out at a lower conveying speed to adjust the effective stretching span.

Comparative Examples 1 to 5

For comparison, the roll-shaped cellulose acetate propionate unstretched film prepared in the above Examples 1 to 6 was unrolled and MD stretching was performed in the MD stretching zone 20. The MD stretching conditions were set forth in the following Table 2 MD stretching of the cellulose acetate propionate unstretched film was carried out in the same manner as in the case of Examples 1 to 6 except that any one of the stretching conditions was outside the scope of the present invention.

Evaluation of MD stretched film

Next, the results of width shrinkage (mm) after stretching of the cellulose acetate propionate film stretched by MD in Examples 1 to 6 and Comparative Examples 1 to 5 are shown in Table 2 below.

Further, the film thickness deviation (占 퐉) after stretching was measured at a distance of 10 mm on the entire width of the film using a contact type film thickness meter, and the maximum film thickness and the minimum film thickness Were evaluated.

The evaluation of the orientation unevenness of the film after MD stretching was carried out by cutting the cellulose acetate propionate film after MD stretching in Examples 1 to 6 and Comparative Examples 1 to 5 by 500 mm in the longitudinal direction and measuring light leakage under cross- , And the results obtained are shown in Table 2 below.

○: Film without light leakage

△: It seems like some unevenness, but the acceptable level of film

X: Film with light leakage

As is clear from the results of Table 2, the cellulose acetate propionate films obtained in Examples 1 to 6 of the present invention all have a very small film thickness deviation after stretching, and even if a film cast with a middle thick film has a final film thickness The shape can be made flat, and a film having good planarity can be obtained. Further, in Example 6, since the stretching span is long, the influence of the width shrinkage extends to the center, and the difference in film thickness between the end portion and the center becomes slightly large. In addition, if the stretching span is long, the width restricting force during stretching becomes weak, unstretched stretching occurs, and the orientation unevenness is slightly lowered.

In the evaluation of the orientation unevenness of the film, all of the cellulose acetate propionate films obtained in Examples 1 to 6 of the present invention were free from light leakage and had excellent optical characteristics. In recent years, the protective films for liquid crystal polarizing plates have been thinned, Which can sufficiently cope with the demands for wider and higher quality.

On the other hand, in the cellulose acetate propionate films obtained in Comparative Examples 1 to 5, the end portions of the cellulose acetate propionate film were strongly pressed against each other by the warp of the touch roll accompanied by the wide width, and the nip pressures at the center became weak , The orientation unevenness of the U-shape was generated in the width direction. In evaluation of the orientation unevenness of the film, there was light leakage and optical characteristics were poor. In the comparative example 2, by making the center thick, the warp of the touch roll accompanying the wide width can be absorbed and the nip can be uniformly pressed in the width direction, so that the orientation becomes uniform in the width direction. However, since the film is not stretched, the thick film remains and can not be used as a product. In Comparative Example 3, since the film before stretching was flat, the MD became thinner at the center, resulting in poor quality. In Comparative Example 4, since the difference in film thickness is excessively large, a difference in principal speed occurs between a thick portion and a thin portion at the time of clamping and pressing, resulting in a nonuniform orientation of stripe shape. In Comparative Example 5, since the stretching magnification was large, the MD thinning became thinner at the center, and the film thickness deviation after stretching was large, and orientation non-uniformity also occurred.

Using the optical films prepared in Examples 1 to 6 and Comparative Examples 1 to 5, a polarizing plate was prepared as follows, and the polarizing plate was inserted into a liquid crystal display panel (image display device) to evaluate the visibility.

Using one of the optical films of Examples 1 to 6 and Comparative Examples 1 to 5 and one of KC8UCR5 (manufactured by Konica Minolta Opto Kabushiki Kaisha) as a cellulose ester optical compensation film as a polarizing plate protective film according to the following method, The polarizing plate of the invention and the polarizing plate of the comparative example were produced.

(a) Production of a polarizing film

100 parts by weight of polyvinyl alcohol (hereinafter abbreviated as PVA) having a degree of saponification of 99.95 mol% and a degree of polymerization of 2400 was impregnated with 10 parts by weight of glycerin and 170 parts by weight of water and melt-kneaded. After defoaming, Followed by melt extrusion. Thereafter, the PVA film was obtained by drying and heat treatment. The obtained PVA film had an average thickness of 40 탆, a water content of 4.4%, and a film width of 3 m.

Next, the PVA film was continuously treated in the order of the following preliminary swelling, dyeing, uniaxial stretching by a wet method, fixing treatment, drying and heat treatment to prepare a polarizing film film.

The PVA film was preliminarily swollen by immersing in water at 30 DEG C for 30 seconds and immersed in an aqueous solution having an iodine concentration of 0.4 g / liter and a potassium iodide concentration of 40 g / liter at 35 DEG C for 3 minutes. Subsequently, uniaxial stretching was carried out in an aqueous solution having a boric acid concentration of 4% at a temperature of 50 DEG C under a tension applied to the film of 700 N / m under a condition of a factor of 6, whereby a potassium iodide concentration of 40 g / liter, a boric acid concentration of 40 g / Liter of aqueous solution at 30 캜 for 5 minutes to carry out fixation treatment. Thereafter, the PVA film was taken out, hot-air dried at 40 占 폚, and heat-treated at 100 占 폚 for 5 minutes. The obtained polarizing film had an average thickness of 13 탆, a transmittance of 43.0%, a polarization degree of 99.5% and a dichroic ratio of 40.1 for the polarizing performance.

(b) Production of polarizing plate

Subsequently, according to the following steps 1 to 5, the polarizing film and the polarizing plate protective film were bonded to each other to produce the polarizing plate of the present invention and the polarizing plate of the comparative example.

Step 1: The optical compensation film and the optical film were immersed in a 3 mol / L sodium hydroxide solution at 60 캜 for 90 seconds, followed by washing with water and drying.

Similarly, the optical compensation film was immersed in a 3 mol / L sodium hydroxide solution at a temperature of 60 DEG C for 90 seconds, followed by washing with water and drying.

Step 2: The above-mentioned polarizing film film was immersed for 1 to 2 seconds in a polyvinyl alcohol bonding preparation with a solid content of 2% by weight.

Step 3: In step 2, the excessive adhesive adhered to the polarizing film film was lightly removed, and then laminated with the optical compensation film sandwiched between the optical compensation film and the alkali-treated film in step 1.

Step 4: bonded at a speed of about 2 m / min with a pressure of 20 to 30 N / cm ² by two rotating rollers. At this time, care was taken to prevent air bubbles from entering.

Step 5: The sample prepared in Step 4 was dried for 2 minutes in a dryer at a temperature of 80 캜 to prepare a polarizing plate.

The polarizing plate on the outermost surface of the commercially available liquid crystal display panel (VA type) was carefully peeled off, and the polarizing plate of the present invention and the polarizing plate of the comparative example were attached thereto.

(Visibility evaluation)

The liquid crystal panel of the present invention and the liquid crystal panel of the comparative example obtained as described above were placed on a table having a height of 80 cm from the bottom and a ceiling part of 3 m height from the floor was exposed to daylight fluorescent light (FLR40S D / MX Matsushita Den- 10 pieces of 40 W x 2 pieces were arranged at 1.5 m intervals. At this time, when the evaluator is on the front face of the liquid crystal panel display face, the fluorescent lamp is arranged on the ceiling portion from the two sides of the evaluator toward the rear. The liquid crystal panel was tilted 25 ° from the vertical direction with respect to the desk so that a fluorescent lamp could be captured so that the visibility (visibility) of the screen was classified and evaluated as follows.

A: You can read letters of font size 8 or less without worrying about the nearest fluorescent light being shot.

B: The slight fluorescent light is a bit of a nuisance, but I do not care much about it, and I can read some characters with font size 8 or less.

C: It is quite troublesome to shoot distant fluorescent light, and it is difficult to read characters of font size 8 or less

D: Fluorescent light is very concerned, and the part that is shot can not read characters of font size 8 or less

As a result of the evaluation, all of the liquid crystal panels into which the polarizing plate using the optical film produced in Examples 1 to 6 of the present invention were inserted were evaluated as B grade or higher, which was good. On the contrary, the liquid crystal panels in which the polarizing plates using the optical films prepared in Comparative Examples 1 to 5 were inserted were all of the evaluation results of C or lower.

1: extruder
2: Filter
3: Static Mixer
4: Flexible die
5: First cooling roll (first cooling first)
6: touch roll (pressurized second rotating body)
7: Second cooling roll (third rotating body for cooling)
8: Third cooling roll (fourth cooling for cooling)
P1: The point at which the film first contacts the surface of the first cooling roll
P2: Point at which the film contacts the touch roll surface
9: peeling roll
10: Film
10a:
10b: film end
11: Burr at the end of the web at the time of casting
12: width stretching device
13: Slitter
14: Embossing ring
15: back roll
16: retractor
F: Optical film (circular wound body)
20: MD stretching band
21: Preheating roll before the first stretching
22: Preheating roll before the second stretching
23: Preheat roll before the third stretch
24: Preheating roll before the fourth stretching
25: stretching / preheating roll
26: nip roll
27: stretching / cooling roll
28: Nip roll
29: After the first stretching,
30: After the second stretching, the cooling roll
31: cooling roll after the third stretching
32: Upper heating heater
33: Lower heating heater
41: guide roll
42: guide roll
S: real stretch span

Claims (7)

An extrusion process for extruding a melt containing a thermoplastic resin from the flexible die into a film form, a nip pressurizing process for nip-pressing the extruded film-like melt (web) between the cooling roll and the touch roll, A method for producing an optical film by a melt soft film forming method comprising a MD stretching step of stretching in the longitudinal direction,
In the MD stretching process,
The unstretched film after the nip press was stretched to 1.1 times or more and 3.0 times or less in the conveying direction (MD direction) of the same film,
In the extrusion step,
The relationship of 10 占 퐉? T1-T2? 200 占 퐉 is established between the film thickness T1 (占 퐉) at the widthwise central portion of the extruded web and the film thickness T2 (占 퐉) at both ends in the width direction of the same web Wherein the optical film has a thickness of 10 to 100 nm. The film stretching method according to claim 1, wherein the stretching method of the film in the MD stretching step is a roll stretching method performed between two adjacent transport rolls, wherein the film is heated and softened by heater heating, And MD stretching is performed at a span of 50 mm or more and 300 mm or less. The method for producing an optical film according to claim 1 or 2, wherein in the nip pressurizing step, the touch roll is formed of an elastic roll having a thin metal plate coated on its peripheral surface. The method for producing an optical film according to claim 1 or 2, wherein the thermoplastic resin is a cellulose ester. An optical film produced by the method for producing an optical film according to claim 1 or 2. A polarizing plate characterized by using the optical film according to claim 5 on one side. A display device using the polarizing plate according to claim 6.

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